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SPECIES  AND  VARIETIES 
Their  Origin  by  Mutation 


Species  and  Varieties 

Their  Origin  by 
Mutation 

Lectures  Delivered  at  the  University  of 

California 

by 

Hugo   DeVries 

Professor  of  Botany  in  the  University  of  Amsterdam 


Edited  by 
Daniel  Trembly   MacDougal 

Director  Department  of  Botanical  Research,  Carnegie  Institution 

of  Washington 


Second  Edition, 
Corrected  and  Revised 


CHICAGO 
The  Open  Court  Publishing  Company 

LONDON 
Kegan  Paul,  Trench,  Trubner  &  Co.,  Ltd. 

1906 


Copyright  1904 

BY 

The  Open  Court  Pub.  Co. 
Chicago 


THE  ORIGIN  OF  SPECIES 


The  origin  of  species  is  a  natural  phenomenon, 

Lamarck. 

The  origin  of  species  is  an  ohject  of  inquiry. 

Darwin. 

The  origin  of  species  is  an  object  of  experi- 
mental investigation.  DeYries. 


PREFACE  BY  THE  AUTHOR 

The  purpose  of  these  lectures  is  to  point  out  the  means 
and  methods  by  which  the  origin  of  species  and  varieties 
may  become  an  object  for  experimental  inquiry,  in  the 
interest  of  agricultural  and  horticultural  practice  as  well 
as  in  that  of  general  biologic  science.  Comparative 
studies  have  contributed  all  the  evidence  hitherto  adduced 
for  the  support  of  the  Darwinian  theory  of  descent  and 
given  us  some  general  ideas  about  the  main  lines  of  the 
pedigree  of  the  vegetable  kingdom,  but  the  way  in  which 
one  species  originates  from  another  has  not  been  ade- 
quately explained.  The  current  belief  assumes  that  spe- 
cies are  slowly  changed  into  new  types.  In  contradiction 
to  this  conception  the  theory  of  mutation  assumes  that 
new  species  and  varieties  are  produced  from  existing 
forms  by  sudden  leaps.  The  parent-type  itself  remains 
unchanged  throughout  this  process,  and  may  repeatedly 
give  birth  to  new  forms.  These  may  arise  simultaneously 
and  in  groups  or  separately  at  more  or  less  widely  dis- 
tant periods. 

The  principal  features  of  the  theory  of  mutation  have 
been  dealt  with  at  length  in  my  book  "  Die  Mutations- 
theorie"  (Vol.  I.,  1901,  Vol.  IL,  1903.  Leipsic,  Veit 
&  Co.),  in  which  I  have  endeavored  to  present  as  com- 
pletely as  possible  the  detailed  evidence  obtained  from 
trustworthy  historical  records,  and  from  my  own  experi- 
mental researches,  upon  which  the  theory  is  based. 

The  University  of  California  invited  me  to  deliver  a 
series  of  lectures  on  this  subject,  at  Berkeley,  during  the 

•  • 

Vll 


viii  Preface  by  the  Author 

summer  of  1904,  and  these  lectures  are  offered  in  this 
form  to  a  public  now  thoroughly  interested  in  the  pro- 
gress of  modern  ideas  on  evolution.  Some  of  my  experi- 
ments and  pedigree-cultures  are  described  here  in  a  man- 
ner similar  to  that  used  in  the  "  Mutationstheorie,"  but 
partly  abridged  and  partly  elaborated,  in  order  to  give  a 
clear  conception  of  their  extent  and  scope.  New  experi- 
ments and  observations  have  been  added,  and  a  wider 
choice  of  the  material  afforded  by  the  more  recent  cur- 
rent literature  has  been  made  in  the  interest  of  a  clear 
representation  of  the  leading  ideas,  leaving  the  exact  and 
detailed  proofs  thereof  to  the  students  of  the  larger  book. 

Scientific  demonstration  is  often  long  and  encumbered 
with  difficult  points  of  minor  importance.  In  these  lec- 
tures I  have  tried  to  devote  attention  to  the  more  im- 
portant phases  of  the  subject  and  have  avoided  the  de- 
tails of  lesser  interest  to  the  general  reader. 

Considerable  care  has  been  bestowed  upon  the  indica- 
tion of  the  lacunae  in  our  knowledge  of  the  subject  and 
the  methods  by  which  they  may  be  filled.  Many  inter- 
esting observations  bearing  upon  the  little  known  parts 
of  the  subject  may  be  made  with  limited  facilities,  either 
in  the  garden  or  upon  the  wild  flora.  Accuracy  and  per- 
severance, and  a  warm  love  for  Nature's  children  are 
here  the  chief  requirements  in  such  investigations. 

In  his  admirable  treatise  on  Evolution  and  Adaptation 
(New  York,  Macmillan  &  Co.,  1903),  Thomas  Hunt  Mor- 
gan has  dealt  in  a  critical  manner  with  many  of  the 
speculations  upon  problems  subsidiary  to  the  theory  of 
descent,  in  so  convincing  and  complete  a  manner,  that  I 
think  myself  justified  in  neglecting  these  questions  here. 
His  book  gives  an  accurate  survey  of  them  all,  and  is 
easily  understood  by  the  general  reader. 

In  concluding  I  have  to  offer  my  thanks  to  Dr.  D.  T. 
MacDougal  and  Miss  A.  M.  Vail  of  the  New  York  Botan- 
ical Garden  for  their  painstaking  work  in  the  prepara- 
tion of  the  manuscript  for  the  press.    Dr.  MacDougal,  by 


Preface  by  the  Author  ix 

his  publications,  has  introduced  my  results  to  his  Ameri- 
can colleagues,  and  moreover  by  his  cultures  of  the  muta- 
tive species  of  the  great  evening-primrose  has  con- 
tributed additional  proof  of  the  validity  of  my  views, 
which  will  go  far  to  obviate  the  difficulties,  which  are 
still  in  the  way  of  a  more  universal  acceptation  of  the 
theory  of  mutation.  My  work  claims  to  be  in  full  ac- 
cord with  the  principles  laid  down  by  Darwin,  and  to  give 
a  thorough  and  sharp  analysis  of  some  of  the  ideas  of 
variability,  inheritance,  selection,  and  mutation,  which 
were  necessarily  vague  at  his  time.  It  is  only  just  to 
state,  that  Darwin  established  so  broad  a  basis  for  scien- 
tific research  upon  these  subjects,  that  after  half  a  century 
many  problems  of  major  interest  remain  to  be  taken  up. 
The  work  now  demanding  our  attention  is  manifestly  that 
of  the  experimental  observation  and  control  of  the  origin 
of  species.  The  principal  object  of  these  lectures  is  to 
secure  a  more  general  appreciation  of  this  kind  of  work. 

Hugo  de  Vries. 
Amsterdam,  Octoher,  190 J^. 


PREFACE  BY  THE  EDITOE 

Professor  de  Vries  has  rendered  an  additional  service 
to  all  naturalists  by  the  preparation  of  the  lectures  on 
mutation  published  in  the  present  volume.  A  perusal  of 
the  lectures  will  show  that  the  subject-matter  of  "Die 
Mutationstheorie "  has  been  presented  in  a  somewhat 
condensed  form,  and  that  the  time  which  has  elapsed 
since  the  original  was  prepared  has  given  opportunity  for 
the  acquisition  of  additional  facts,  and  a  re-examination 
of  some  of  the  more  important  conclusions  with  the  re- 
sult that  a  notable  gain  has  been  made  in  the  treatment 
of  some  complicated  problems. 

It  is  hoped  that  the  appearance  of  this  English  version 
of  the  theory  of  mutation  will  do  much  to  stimulate  in- 
vestigation of  the  various  phases  of  the  subject.  This 
volume,  however,  is  by  no  means  intended  to  replace,  as  a 
work  of  reference,  the  larger  book  with  its  detailed  recital 
of  facts  and  its  comprehensive  records,  but  it  may  prove 
a  substitute  for  the  use  of  the  general  reader. 

The  revision  of  the  lectures  has  been  a  task  attended 
with  no  little  pleasure,  especially  since  it  has  given  the 
editor  the  opportunity  for  an  advance  consideration  of 
some  of  the  more  recent  results,  thus  materially  facilitat- 
ing investigations  which  have  been  in  progress  at  the 
New  York  Botanical  Garden  for  some  time.  So  far  as 
the  ground  has  been  covered  the  researches  in  question 
corroborate  the  conclusions  of  de  Vries  in  all  important 
particulars.  The  preparation  of  the  manuscript  for  the 
printer  has  consisted  chiefly  in  the  adaptation  of  oral 


xii  Preface  by  the  Editor 

discussions  and  demonstrations  to  a  form  suitable  for 
permanent  record,  together  with  certain  other  alterations 
which  have  been  duly  submitted  to  the  author.  The 
original  phraseology  has  been  preserved  as  far  as  pos- 
sible. The  editor  wishes  to  acknowledge  material  as- 
sistance in  this  work  from  Miss  A.  M.  Vail,  Librarian  of 
the  New  York  Botanical  Garden. 

D.  T.  MacDougal. 

New  York  Botanical  Garden,  Octoher,  190J^, 


PREFACE  TO  THE  SECOND  EDITION. 

The  constantly  increasing  interest  in  all  phases  of  evo- 
lution has  made  necessary  the  preparation  of  a  second 
edition  of  this  book  within  a  few  months  after  the  first 
appeared.  The  opportunity  has  been  used  to  eliminate 
typographical  errors,  and  to  make  alterations  in  the  form 
of  a  few  sentences  for  the  sake  of  clearness  and  smooth- 
ness. The  subject  matter  remains  practically  unchanged. 
An  explanatory  note  has  been  added  on  page  575  in  order 
to  avoid  confusion  as  to  the  identity  of  some  of  the  plants 
which  figure  prominently  in  the  experimental  investiga- 
tions in  Amsterdam  and  New  York. 

The  portrait  which  forms  the  frontispiece  is  a  repro- 
duction of  a  photograph  taken  by  Professor  F.  E.  Lloyd 
and  Dr.  W.  A.  Cannon  during  the  visit  of  Professor  de 
Vries  at  the  Desert  Botanical  Laboratory  of  the  Carnegie 
Institution,  at  Tucson,  Arizona,  in  June,  1904. 

D.  T.  MacDougal. 

December  15,  1905, 


CONTENTS 

A.    Introduction. 
Lecture  Page 

I.    Descent :  theories  of  evolution  and  methods 

of  investigation 1 

The  theory  of  descent  and  of  natural  se- 
lection.       Evolution      and      adaptation. 
Elementary  species  and  varieties.    Meth- 
ods of  scientific  pedigree-culture. 

B.    Elementary  Species. 

II.     Elementary    species   in   nature     ...       32 
Viola     tricolor,     Draba     verna.     Primula 
acaulis,  and  other  examples.     Euphorbia 
Ipecacuanha.  Prunus  maritima.  Taraxa- 
cum and  Hieracium. 

III.  Elementary  species  of  cultivated  plants.      63 
Beets,  apples,  pears,  clover,  flax  and  coco- 
nut. 

IV.  Selection  of  elementary  species     ...       92 

Cereals.  Le  Couteur.  Running  out  of 
varieties.  Rimpau  and  Risler,  Aveiia  fa- 
tua.  Meadows.  Old  Egyptian  cereals. 
Selection  by  the  Romans.    Shirreff.    Hays. 

C.    Retrograde  Varieties. 

V.     Characters  of  retrograde  varieties     .     .     121 
Seed  varieties  of  pure,  not  hybrid  origin. 
Differences     from     elementary     species. 
Latent  characters.    Ray-florets  of  com- 
xiii 


XIV  Contents 

Lecture  Page 

posites.  Progressive  red  varieties.  Ap- 
parent losses.  Xanthium  canadense. 
Correlative  variability.  Laciniate  leaves 
and  petals.     Compound  characters. 

VI.     Stability  and   real   atavism     ....     154 
Constancy  of  retrograde  varieties.     Atav- 
ism  in   Ribes    sanguineum   albidum,   in 
conifers,   in  Iris  pallida.      Seedlings  of 
Acacia.    Eeversion  by  buds. 

VII.  Ordinary  or  false  atavism  ....  185 
Vicinism  or  variation  under  the  influence 
of  pollination  by  neighboring  individ- 
uals. Vicinism  in  nurseries.  Purify- 
ing new  and  old  varieties.  A  case  of 
running  out  of  corn  in  Germany. 

VIII.    Latent  characters 216 

Leaves  of  seedlings,  adventitious  buds,  sys- 
tematic latency  and  retrogressive  evolu- 
tion. Degressive  evolution.  Latency 
of  specific  and  varietal  characters  in 
wheat-ear  carnation,  in  the  green  dahlias, 
in  white  campanulas  and  others.  System- 
atic latency  of  flower  colors. 

IX.  Crossing  of  species  and  varieties  .  .  247 
Balanced  and  unbalanced,  or  species  and 
variety  crosses.  Constant  hybrids  of 
Oenothera  muricata  and  0.  biennis. 
Aegilops,  Medicago,  brambles  and  other 
instances. 

X.    MendePs    law    of   balanced    crosses    .    .    276 
Pairs   of  antagonistic   characters,   one  ac- 
tive  and   one  latent.    Papaver   somnif- 


Contents 


XV 


Lecture  Page 

erum  Mephisto  Danebrog.  Mendel's  laws. 
Unit-characters. 

D.      EVERSPORTING  VARIETIES. 

XI.     Striped  flowers 309 

Antirrhinum  majus  luteum  rubro-striatum 
with    pedigree.     Striped    flowers,    fruits 
and  radishes.    Double  stocks. 
XII.    "  Five  leaved "  clover 340 

Origin  of  this  variety.  Periodicity  of  the 
anomaly.    Pedigree-cultures.     Ascidia. 

Xm.    Polycephalic   poppies 369 

Permanency  and  high  variability.  Sensi- 
tive period  of  the  anomaly.  Depend- 
ency on  external  conditions. 

XIV.    Monstrosities        400 

Inheritance  of  monstrosities.  Half  races 
and  middle  races.  Hereditary  value  of 
atavists.  Twisted  stems  and  fascia- 
tions.  Middle  races  of  trieotyls  and 
syncotyls.  Selection  by  the  hereditary 
percentage  among  the  offspring. 

XV.    Double  adaptations        430 

Analogy  between  double  adaptations  and 
anomalous  middle  races.  Polygonum 
amphibium.  Alpine  plants.  Othonna 
crassifolia.  Leaves  in  sunshine  and 
shadow.  Giants  and  dwarfs.  Figs  and 
ivy.    Leaves  of  seedlings. 

E.    Mutations. 

XVI.     Origin  of  the  peloric  toad-flax     .     .     .     459 
Sudden  and  frequent  origin  in  the  wild 
state.     Origin  in  the  experiment-garden. 
Law    of    repeated    mutations.     Probable 
origin  of  other  pelories. 


xvi  Contents 

Lecture  Page 

XVII.  The  production  of  double  flowers  .  .  488 
Sudden  appearance  of  double  flowers  in 
horticulture.  Historical  evidence.  Ex- 
perimental origin  of  Chrysanthemum 
segetum  plenum.  Dependency  upon 
nourishment.    Petalody  of  stamens. 

XVIII.  New  species  of  Oenothera  ....  516 
Mutations  of  Oenothera  lamarckiana  in 
the  wild  state  near  Hilversum.  New 
varieties  of  0.  laevifolia,  O.  brevistylis, 
and  O.  nanella.  New  elementary  species, 
O.  gigas,  O.  rubrinervis,  albida,  and  ob- 
longa.  O.  lata  a  pistillate  form.  In- 
constancy of  O.  scintillans. 

XIX.  Experimental  pedigree-cultures  .  .  .  547 
Pedigree  of  the  mutative  products  of 
Oenothera  lamarckiana  in  the  Botan- 
ical Garden  at  Amsterdam.  Laws  of 
mutability.  Sudden  and  repeated  leaps 
from  an  unchanging  main  strain.  Con- 
stancy of  the  new  forms.  Mutations  in 
all  directions. 

XX.  Origin  of  wild  species  and  varieties  .  .  576 
Problems  to  solve.  Capsella  heegeri. 
Oenothera  biennis  cruciata.  Epilobium 
hirsutum  cruciatum.  Hibiscus  Mos- 
cheutos.  Purple  beech.  Monophyllous 
strawberries.  Chances  of  success  with 
new  mutations. 

XXI.     Mutations  in  horticulture       ....     604 
Chelidonium  majus  lacinatum.    Dwarf  and 
spineless     varieties.       Laciniate     leaves. 
Monophyllous   and  broom-like  varieties. 


Contents 


xvii 


Lecture 


Page 
Purple  leaves.     Celosia.     Italian  poplar. 
Cactus  dahlia.    Mutative  origin  of  Dah- 
lia fistulosa,  and  Geranium  pratense  in 
the  experiment-garden. 


XXII. 


Systematic  atavism 
Reappearance     of 

Primula    acaulis 

crucifers.       Zea 

Equisetum,    Dipsacus    sylvestris 

Tomatoes. 


630 


ancestral      characters. 

umbellata.     Bracts    of 

Mays      cryptosperma. 

torsus. 


XXIII. 


Taxonomic  anomalies 658 

Specific  characters  occurring  in  other  cases 
as  casual  anomalies.  Papaver  brac- 
teatum  monopetalum.  Desmodium 
gyrans  and  monophyllous  varieties.  Pel- 
tate leaves  and  ascidia.  Flowers  on 
leaves.    Leaves.    Hordeum  trifurcatum. 


XXIV.     Hypothesis  of  periodical  mutations  .     .     686 
Discovering   mutable    strains.    Periods    of 
mutability    and    constancy.     Periods    of 
mutations.     Genealogical  trees.     Limited 
life-time  of  the  organic  kingdom, 

F.    Fluctuations. 

XXV.     General  laws  of  fluctuations     ....     715 
Fluctuating    variability.      Quetelet's    law. 
Individual      and      partial      fluctuations. 
Linear  variability.     Influence  of  nutri- 
tion.    Periodicity-curves. 

XXVI.     Asexual  multiplication  of  extremes    .     .     742 
Selection    between    species    and    intra-spe- 
cific     selection.       Excluding     individual 


xviii  Contents 

Lecture  Page 

and  embryonic  variability.  Sugar-canes. 
Flowering  cannas.  Double  lilacs.  Other 
instances.  Burbank's  method  of  selec- 
tion. 

XXVII.  Inconstancy  of  improved  races  .  .  .  770 
Larger  variability  in  the  case  of  propaga- 
tion by  seed.  Progression  and  regres- 
sion after  a  single  selection,  and  after 
repeated  selections.  Selection  experi- 
ments with  corn.  Advantages  and  effect 
of  repeated  selection. 

XXVIII.  Artificial  and  natural  selection  .  ,  .  798 
Conclusions.  Specific  and  intra-specific 
selection.  Natural  selection  in  the  field. 
Acclimatization.  Improvement-selection 
of  sugar-beets  by  various  methods.  Rye. 
Hereditary  percentage  and  centgener 
power  as  marks  by  which  intra-specific 
selection  may  be  guided. 

Index         827 


A.    INTRODUCTION 
Lecture  I 

DESCENT :  THEORIES  OF  EVOLUTIOIT,   AND   METHODS 

OF   INVESTIGATION 

Newton  convinced  his  contemporaries  that 
natural  laws  rule  the  whole  universe.  Lyell 
showed,  by  his  principle  of  slow  and  gradual 
evolution,  that  natural  laws  have  reigned  since 
the  beginning  of  time.  To  Darwin  we  owe  the 
almost  universal  acceptance  of  the  theory  of 
descent. 

This  doctrine  is  one  of  the  most  noted  land- 
marks in  the  advance  of  science.  It  teaches  the 
validity  of  natural  laws  of  life  in  its  broadest 
sense,  and  crowns  the  philosophy  founded  by 
Newton  and  Lyell. 

Lamarck  proposed  the  hypothesis  of  a  com- 
mon origin  of  all  living  beings  and  this  ingenious 
and  thoroughly  philosophical  conception  was 
warmly  welcomed  by  his  partisans,  but  was  not 
widely  accepted  owing  to  lack  of  supporting  evi- 
dence.    To    Darwin  was  reserved  the  task  of 

1 


frnPERTT  imiuRr 
N.  C.  State  College 


2  Descent 

bringing  the  theory  of  common  descent  to  its 
present  high  rank  in  scientific  and  social  phi- 
losophy. 

Two  main  features  in  his  work  have  contrib- 
uted to  this  early  and  unexpected  victory.  One 
of  them  is  the  almost  unlimited  amount  of  com- 
parative evidence,  the  other  is  his  demonstration 
of  the  possibility  of  a  physiological  explanation 
of  the  process  of  descent  itself. 

The  universal  belief  in  the  independent  crea- 
tion of  living  organisms  was  revised  by 
Linnaeus  and  was  put  upon  a  new  foundation. 
Before  him  the  genera  were  supposed  to  be 
created,  the  species  and  minor  forms  having 
arisen  from  them  through  the  agency  of  ex- 
ternal conditions.  In  his  first  book  Linnaeus 
adhered  to  this  belief,  but  later  changed  his 
mind  and  maintained  the  principle  of  the  sep- 
arate creation  of  species.  The  weight  of  his 
authority  soon  brought  this  conception  to  uni- 
versal acceptance,  and  up  to  the  present  time 
the  prevailing  conception  of  a  species  has  been 
chiefly  based  on  the  definition  given  by  Linnaeus. 
His  species  comprised  subspecies  and  varieties, 
which  were  in  their  turn,  supposed  to  have 
evolved  from  species  by  the  common  method. 

Darwin  tried  to  show  that  the  links  which 
bind  species  to  genera  are  of  the  same  nature 
as  those  which  determine  the  relationship  of 


Theories  of  Evolution  3 

subspecies  and  varieties.  If  an  origin  by  nat- 
ural laws  is  conceded  for  the  latter,  it  must,  on 
this  ground  be  granted  for  the  first  also.  In 
this  discussion  he  simply  returned  to  the  pre- 
Linnean  attitude.  But  his  material  was  such 
as  to  allow  him  to  go  one  step  further,  and  this 
step  was  an  important  and  decisive  one.  He 
showed  that  the  relation  between  the  various 
genera  of  a  family  does  not  exhibit  any  fea- 
tures of  a  nature  other  than  that  between  the 
species  of  a  genus.  What  has  been  conceded 
for  the  one  must  needs  be  accepted  for  the 
other.  The  same  holds  good  for  the  large 
groups.  The  conviction  of  the  common  origin 
of  closely  allied  forms  necessarily  leads  to  the 
conception  of  a  similar  descent  even  in  remote 
relationships. 

The  origin  of  subspecies  and  varieties  as 
found  in  nature  was  not  proved,  but  only  gen- 
erally recognized  as  evident.  A  broader 
knowledge  has  brought  about  the  same  state  of 
opinion  for  greater  groups  of  relationships. 
Systematic  affinities  find  their  one  possible  ex- 
planation by  the  aid  of  this  principle;  without 
it,  all  similarity  is  only  apparent  and  accidental. 
Geographic  and  paleontologic  facts,  brought  to- 
gether by  Darwin  and  others  on  a  previously 
unequalled  scale,  point  clearly  in  the  same  di- 
rection.    The  vast  amount  of  evidence  of  all 


4  Descent 

comparative  sciences  compels  us  to  accept  the 
idea.  To  deny  it,  is  to  give  up  all  oppor- 
tunity of  conceiving  Nature  in  her  true  form. 

The  general  features  of  the  theory  of  descent 
are  now  accepted  as  the  basis  of  all  biological 
science.  Half  a  century  of  discussion  and  in- 
vestigation has  cleared  up  the  minor  points  and 
brought  out  an  abundance  of  facts;  but  they 
have  not  changed  the  principle.  Descent  with 
modification  is  now  universally  accepted  as  the 
chief  law  of  nature  in  the  organic  world.  In 
honor  of  him,  who  with  unsurpassed  genius,  and 
by  unlimited  labor  has  made  it  the  basis  of 
modern  thought,  this  law  is  called  the  ^'  Dar- 
winian theory  of  descent. ' ' 

Darwin's  second  contribution  to  this  attain- 
ment was  his  proof  of  the  possibility  of  a  phys- 
iological explanation  of  the  process  of  descent 
itself.  Of  this  possibility  he  fully  convinced  his 
contemporaries,  but  in  indicating  the  particular 
means  by  which  the  change  of  species  has  been 
brought  about,  he  has  not  succeeded  in  securing 
universal  acceptation.  Quite  on  the  contrary, 
objections  have  been  raised  from  the  very  out- 
set, and  with  such  force  as  to  compel  Darwin 
himself  to  change  his  views  in  his  later  writings. 
This  however,  was  of  no  avail,  and  objections 
and  criticisms  have  since  steadily  accumulated. 

Physiologic  facts  concerning  the  origin  of 


Theories  of  Evolution  5 

species  in  nature  were  unknown  in  the  time  of 
Darwin.  It  was  a  happy  idea  to  choose  the  ex- 
perience of  the  breeders  in  the  production  of 
new  varieties,  as  a  basis  on  whicli  to  build  an 
explanation  of  the  processes  of  nature.  In  my 
opinion  Darwin  was  quite  right,  and  he  has  suc- 
ceeded in  giving  the  desired  proof.  But  the 
basis  was  a  frail  one,  and  would  not  stand  too 
close  an  examination.  Of  this  Darwin  was  al- 
ways well  aware.  He  has  been  prudent  to  the 
utmost,  leaving  many  points  undecided,  and 
among  them  especially  the  range  of  validity  of 
his  several  arguments.  Unfortunately  this 
prudence  has  not  been  adopted  by  his  followers. 
Without  sufficient  warrant  they  have  laid  stress 
on  one  phase  of  the  problem,  quite  overlooking 
the  others.  Wallace  has  even  gone  so  far  in  his 
zeal  and  ardent  veneration  for  Darwin,  as  to 
describe  as  Darwinism  some  things,  which  in  my 
opinion,  had  never  been  a  part  of  Darwin's  con- 
ceptions. 

The  experience  of  the  breeders  was  quite  in- 
adequate to  the  use  which  Darwin  made  of  it. 
It  was  neither  scientific,  nor  critically  accurate. 
Laws  of  variation  were  barely  conjectured ;  the 
different  types  of  variability  were  only  imper- 
fectly distinguished.  The  breeders'  conception 
was  fairly  sufficient  for  practical  purposes, 
but  science  needed  a  clear  understanding  of  the 


6  Descent 

factors  in  the  general  process  of  variation.  Re- 
peatedly Darwin  tried  to  formulate  these  causes, 
but  the  evidence  available  did  not  meet  his  re- 
quirements. 

Quetelet's  law  of  variation  had  not  yet  been 
published.  Mendel's  claim  of  hereditary  units 
for  the  explanation  of  certain  laws  of  hybrids 
discovered  by  him,  was  not  yet  made.  The 
clear  distinction  between  spontaneous  and  sud- 
den changes,  as  compared  with  the  ever-present 
fluctuating  variations,  is  only  of  late  coming  into 
recognition  by  agriculturists.  Innumerable 
minor  points  which  go  to  elucidate  the  breeders ' 
experience,  and  with  which  we  are  now  quite 
familiar,  were  unknown  in  Darwin's  time.  No 
wonder  that  he  made  mistakes,  and  laid  stress 
on  modes  of  descent,  which  have  since  been 
proved  to  be  of  minor  importance  or  even  of 
doubtful  validity. 

Notwithstanding  all  these  apparently  unsur- 
mountable  difficulties,  Darwin  discovered  the 
great  principle  which  rules  the  evolution  of  or- 
ganisms. It  is  the  principle  of  natural  selec- 
tion. It  is  the  sifting  out  of  all  organisms  of 
minor  worth  through  the  struggle  for  life.  It 
is  only  a  sieve,  and  not  a  force  of  nature,  not  a 
direct  cause  of  improvement,  as  many  of  Dar- 
win's adversaries,  and  unfortunately  many  of 
his  followers  also,  have  so  often  asserted.    It  is 


Theories  of  Evolution  7 

only  a  sieve,  which  decides  what  is  to  live,  and 
what  is  to  die.  But  evolutionary  lines  are  of 
great  length,  and  the  evolution  of  a  flower,  or  of 
an  insectivorous  plant  is  a  way  with  many  side- 
paths.  It  is  the  sieve  that  keeps  evolution  on 
the  main  line,  killing  all,  or  nearly  all  that  try 
to  go  in  other  directions.  By  this  means  nat- 
ural selection  is  the  one  directing  cause  of  the 
broad  lines  of  evolution. 

Of  course,  with  the  single  steps  of  evolution 
it  has  nothing  to  do.  Only  after  the  step  has 
been  taken,  the  sieve  acts,  eliminating  the  unfit. 
The  problem,  as  to  the  manner  in  which  the  in- 
dividual steps  are  brought  about,  is  quite  an- 
other side  of  the  question. 

On  this  point  Darwin  has  recognized  two  pos- 
sibilities. One  means  of  change  lies  in  the  sud- 
den and  spontaneous  production  of  new  forms 
from  the  old  stock.  The  other  method  is  the 
gradual  accumulation  of  those  always  present 
and  ever  fluctuating  variations  which  are  in- 
dicated by  the  common  assertion  that  no  two 
individuals  of  a  given  race  are  exactly  alike. 
The  first  changes  are  what  we  now  call  ' '  muta- 
tions," the  second  are  designated  as  "  individ- 
ual variations,"  or  as  this  term  is  often  used  in 
another  sense,  as  ^^  fluctuations."  Darwin  rec- 
ognized both  lines  of  evolution;  Wallace  disre- 
garded the  sudden  changes  and  propo.sed  fluctu- 


8  Descent 

ations  as  the  exclusive  factor.  Of  late,  however, 
this  point  of  view  has  been  abandoned  by  many 
investigators,  especially  in  America. 

The  actual  occurrence  of  mutations  is  now 
recognized,  and  the  battle  rages  about  the  ques- 
tion, as  to  whether  they  are  be  regarded  as  the 
principal  means  of  evolution,  or,  whether  slow 
and  gradual  changes  have  not  also  played  a 
large  and  important  part. 

The  defenders  of  the  theory  of  evolution  by 
slow  accumulation  of  slight  fluctuations  are  di- 
vided into  two  camps.  One  group  is  called  the 
Neo-Lamarckians ;  they  assume  a  direct  modi- 
fying agency  of  the  environment,  producing  a 
corresponding  and  useful  change  in  the  organ- 
ization. The  other  group  call  themselves  Dar- 
winians or  selectionists,  but  to  my  mind  with 
no  other  right  beyond  the  arbitrary  restriction 
of  the  Darwinian  principles  by  Wallace.  They 
assume  fluctuating  variations  in  all  directions 
and  leave  the  choice  between  them  to  the  sieve 
of  natural  selection. 

Of  course  we  are  far  from  a  decision  between 
these  views,  on  the  sole  ground  of  the  facts  as 
known  at  present.  Mutations  under  observa- 
tion are  as  yet  very  rare;  enough  to  indicate 
the  possible  and  most  probable  ways,  but  no 
more.  On  the  other  hand  the  accumulation  of 
fluctuations  does  not  transgress  relatively  nar- 


Theories  of  Evolution  9 

row  limits  as  far  as  the  present  methods  of 
selection  go.  But  the  question  remains  to  be 
solved,  whether  our  methods  are  truly  the  right 
ones,  and  whether  by  the  use  of  new  princi- 
ples, new  results  might  not  cause  the  balance  of 
opinion  to  favor  the  opposite  side. 

Of  late,  a  thorough  and  detailed  discussion  of 
the  opposing  views  has  been  given  by  Morgan 
in  his  valuable  book  on  evolution  and  adapta- 
tion. He  has  subjected  all  the  proposed  theo- 
ries to  a  severe  criticism  both  on  the  ground  of 
facts  and  on  that  of  their  innate  possibility  and 
logical  value.  He  decides  in  favor  of  the  mu- 
tation-theory. His  arguments  are  incisive  and 
complete  and  wholly  adapted  to  the  compre- 
hension of  all  intelligent  readers,  so  that  his 
book  relieves  me  entirely  of  the  necessity  of 
discussing  these  general  questions,  as  it  could 
not  be  done  in  a  better  or  in  a  clearer  way. 

I  intend  to  give  a  review  of  the  facts  obtained 
from  plants  which  go  to  prove  the  assertion, 
that  species  and  varieties  have  originated  by 
mutation,  and  are,  at  present,  not  known  to  orig- 
inate in  any  other  way.  This  review  consists 
of  two  parts.  One  is  a  critical  survey  of  the 
facts  of  agricultural  and  horticultural  breed- 
ing, as  they  have  accumulated  since  the  time  of 
Darwin.  This  bodv  of  evidence  is  to  be  com- 
bined    with    some    corresponding   experiments 


10  Descent 

concerning  the  real  nature  of  species  in  the  wild 
state.  The  other  part  rests  on  my  own  obser- 
vations and  experiments,  made  in  the  botanical 
garden  of  the  University  of  Amsterdam. 

For  many  years  past  I  have  tried  to  elucidate 
the  hereditary  conditions  of  species  and  varie- 
ties, and  the  occasional  occurrence  of  mutations, 
that  suddenly  produce  new  forms. 

The  present  discussion  has  a  double  purpose. 
On  one  side  it  will  give  the  justification  of  the 
theory  of  mutations,  as  derived  from  the  facts 
now  at  hand.  On  the  other  hand  it  will  point 
out  the  deficiencies  of  available  evidence,  and 
indicate  the  ways  by  which  the  lacunae  may 
gradually  be  filled.  Experimental  work  on 
heredity  does  not  require  vast  installments  or 
a  costly  laboratory  equipment.  It  demands 
chiefly  assiduity  and  exactitude.  Any  one  who 
has  these  two  qualities,  and  who  has  a  small 
garden  at  his  disposal  is  requested  to  take  part 
in  this  line  of  investigation. 

In  order  to  observe  directly  the  birth  of  new 
forms  it  is  necessary,  in  the  first  i3lace,  to  be 
fully  clear  concerning  the  question  as  to  what 
forms  are  to  be  expected  to  arise  from  others, 
and  before  proceeding  to  a  demonstration  of  the 
origin  of  species,  it  is  pertinent  to  raise  the 
question  as  to  what  constitutes  a  species. 

Species  is  a  word,  which  always  has  had  a 


Theories  of  Evolution  11 

double  meaning.  One  is  the  systematic  species, 
which  is  the  unit  of  our  system.  But  these 
units  are  by  no  means  indivisible.  Long  ago 
Linnaeus  knew  them  to  be  compound  in  a  great 
number  of  instances,  and  increasing  knowledge 
has  shown  that  the  same  rule  prevails  in  other 
instances.  Today  the  vast  majority  of  the  old 
systematic  species  are  known  to  consist  of  minor 
units.  These  minor  entities  are  called  varieties 
in  systematic  works.  However,  there  are  many 
objections  to  this  usage.  First,  the  term  vari- 
ety is  applied  in  horticulture  and  agriculture 
to  things  so  widely  divergent  as  to  convey  no 
clear  idea  at  all.  Secondly,  the  subdivisions 
of  species  are  by  no  means  all  of  the  same 
nature,  and  the  svstematic  varieties  include 
units  the  real  value  of  which  is  widely  differ- 
ent in  different  cases.  Some  of  these  vari- 
eties are  in  reality  as  good  as  species,  and 
have  been  *'  elevated,"  as  it  is  called,  by  some 
writers,  to  this  rank.  This  conception  of  the 
elementary  species  would  be  quite  justifiable, 
and  would  at  once  get  rid  of  all  difficulties,  were 
it  not  for  one  practical  obstacle.  The  number 
of  the  species  in  all  genera  would  be  doubled 
and  tripled,  and  as  these  numbers  are  already 
cumbersome  in  many  cases,  the  distinction  of 
the  native  species  of  any  given  country  would 
lose  most  of  its  charm  and  interest. 


12  Descent 

In  order  to  meet  this  difficulty  we  must  recog- 
nize two  sorts  of  species.  The  systematic  spe- 
cies are  the  practical  units  of  the  systematists 
and  florists,  and  all  friends  of  wild  nature 
should  do  their  utmost  to  preserve  them  as 
Linnaeus  has  proposed  them.  These  units  how- 
ever, are  not  really  existing  entities;  they 
have  as  little  claim  to  be  regarded  as  such 
as  genera  and  families.  The  real  units  are 
the  elementary  si3ecies;  their  limits  often  ap- 
parently overlap  and  can  only  in  rare  cases  be 
determined  on  the  sole  ground  of  field-obser- 
vations. Pedigree-culture  is  the  method  re- 
quired and  any  form  which  remains  constant 
and  distinct  from  its  allies  in  the  garden  is  to 
be  considered  as  an  elementary  species. 

In  the  following  lectures  we  shall  con- 
sider this  point  at  length,  to  show  the  compound 
nature  of  systematic  species  in  wild  and  in  culti- 
vated plants.  In  both  cases,  the  principle  is 
becoming  of  great  importance,  and  many  pa- 
pers published  recently  indicate  its  almost  uni- 
versal acceptation. 

Among  the  systematic  subdivisions  of  species, 
not  all  have  the  same  claim  to  the  title  of  ele- 
mentary species.  In  the  first  place  the  cases 
in  which  the  differences  may  occur  between 
parts  of  the  same  individual  are  to  be  excluded. 
Dividing  an  alpine  plant  into  two  halves  and 


Theories  of  Evolution  13 

planting  one  in  a  garden,  varietal  differences 
at  once  arise  and  are  often  designated  in  sys- 
tematic works  under  different  varietal  names. 
Secondly  all  individual  differences  which  are  of 
a  fluctuating  nature  are  to  be  combined  into  a 
group.     But  with  these  we  shall  deal  later. 

Apart  from  these  minor  points  the  subdi- 
visions of  the  systematic  species  exhibit  two 
widely  different  features.  I  will  now  try  to 
make  this  clear  in  a  few  words,  but  will  return 
in  another  lecture  to  a  fuller  discussion  of  this 
most  interesting  contrast. 

Linnaeus  himself  knew  that  in  some  cases  all 
subdivisions  of  a  species  are  of  equal  rank,  to- 
gether constituting  the  group  called  species. 
No  one  of  them  outranks  the  others;  it  is  not 
a  species  with  varieties,  but  a  group  consisting 
only  of  varieties.  A  closer  inquiry  into  the 
cases  treated  in  this  manner  by  the  great  master 
of  systematic  science,  shows  that  here  his  varie- 
ties were  exactly  what  we  now  call  elementary 
species. 

In  other  cases  the  varieties  are  of  a  deriva- 
tive nature.  The  species  constitutes  a  type  that 
is  pure  in  a  race  which  ordinarily  is  still  grow- 
ing somewhere,  though  in  some  cases  it  may 
have  died  out.  From  this  type  the  varieties  are 
derived,  and  the  way  of  this  derivation  is  usual- 
ly quite  manifest  to  the  botanist.     It  is  ordina- 


14  Descent 

rily  by  the  disappearance  of  some  superficial 
character  that  a  variety  is  distinguished  from 
its  species,  as  by  the  lack  of  color  in  the  flowers, 
of  hairs  on  stems  and  foliage,  of  the  spines  and 
thorns,  &c.  Such  varieties  are,  strictly  speak- 
ing, not  to  be  treated  in  the  same  way  as  elemen- 
tary species,  though  they  often  are.  We  shall 
designate  them  by  the  term  of  '^  retrograde 
varieties,''  which  clearlv  indicates  the  nature  of 
their  relationship  to  the  species  from  which  they 
are  assumed  to  have  sprung.  In  order  to  lay 
more  stress  on  the  contrast  between  elementary 
species  and  retrograde  varieties,  it  should  be 
stated  at  once,  that  the  first  are  considered  to 
have  originated  from  their  parent-form  in  a 
progressive  way.  They  have  succeeded  in  at- 
taining something  quite  new  for  themselves, 
while  retrograde  varieties  have  only  thrown 
otf  some  peculiarity,  previously  acquired  by 
their  ancestors. 

The  whole  vegetable  kingdom  exhibits  a  con- 
stant struggle  between  progression  and  retro- 
gression. Of  course,  the  great  lines  of  the  gen- 
eral pedigree  are  due  to  progression,  many 
single  steps  in  this  direction  leading  together  to 
the  great  superiority  of  the  flowering  plants 
over  their  cryptogamous  ancestors.  But  pro- 
gression is  nearly  always  accompanied  by  re- 
trogression  in  the  principal  lines  of  evolution, 


Theories  of  Evolution  15 

as  well  as  in  the  collateral  branches  of  the  gen- 
ealogical tree.  Sometimes  it  prevails,  and 
the  monocotyledons  are  obviously  a  reduced 
branch  of  the  primitive  dicotyledons.  In  or- 
chids and  aroids,  in  grasses  and  sedges,  reduc- 
tion plays  a  most  important  part,  leaving  its 
traces  on  the  flowers  as  well  as  on  the  embryo  of 
the  seed.  Many  instances  could  be  given  to  prove 
that  progression  and  retrogression  are  the  two 
main  principles  of  evolution  at  large.  Hence 
the  conclusion  that  our  analvsis  must  dissect  the 
complicated  phenomena  of  evolution  so  far  as 
to  show  the  separate  functions  of  these  two  con- 
trasting principles.  Hundreds  of  steps  were 
needed  to  evolve  the  family  of  the  orchids,  but 
the  experimenter  must  take  the  single  steps 
for  the  object  of  his  inquiry.  He  finds  that 
some  are  progressive  and  others  retrogressive 
and  so  his  investigation  falls  under  two  heads, 
the  origin  of  progressive  characters,  and  the 
subsequent  loss  of  the  same.  Progressive  steps 
are  the  marks  of  elementary  species,  while  re- 
trograde varieties  are  distinguished  by  ap- 
parent losses.  They  have  equal  claim  to  our 
interest  and  our  study. 

As  already  stated  I  propose  to  deal  first  with 
the  elementary  species  and  afterwards  with  the 
retrograde  varieties.  I  shall  try  to  depict  them 
to  you  in  the  first  place  as  they  are  seen  in 


16  Descent 

nature  and  in  culture,  leaving  tlie  question  of 
their  origin  to  a  subsequent  experimental  treat- 
ment. 

The  question  of  the  experimental  origin  of 
new  species  and  varieties  has  to  be  taken  up 
from  two  widely  separated  starting  points.  This 
may  be  inferred  from  what  we  have  already 
seen  concerning  the  two  opposing  theories,  de- 
rived and  isolated  from  Darwin's  original 
broad  conception.  One  of  them  considers 
mutations  as  the  origin  of  new  forms,  while  the 
other  assumes  fluctuations  to  be  the  source  of 
all  evolution. 

As  mentioned  above,  my  own  experience  has 
led  me  to  accept  the  first  view.  Therefore  I 
shall  have  to  show  that  mutations  do  yield  new 
and  constant  forms,  while  fluctuations  are  not 
adequate  to  do  so.  Retrograde  varieties  and 
elementary  species  may  both  be  seen  to  be 
produced  by  sudden  mutations.  Varieties  have 
often  been  observed  to  appear  at  once  and  quite 
unexpectedly  in  horticulture  and  agriculture, 
and  a  survey  of  these  historical  facts  will  be  the 
subject  of  one  of  my  lectures.  In  some  in- 
stances I  have  succeeded  in  repeating  these 
observations  in  my  garden  under  the  strict  con- 
ditions of  a  scientific  experiment,  and  these  in- 
stances teach  us  the  real  nature  of  the  process 
of  mutation  in  all  its  visible  features.     New  ele- 


Theories  of  Evolution  17 

mentary  species  are  far  more  rare,  but  I  have 
discovered  in  the  great  evening-primrose,  or 
Oenothera  lamarckiana  a  strain  which  is  pro- 
ducing them  yearly  in  the  wild  state  as  well  as 
in  my  garden.  These  observations  and  pedi- 
gree-experiments will  be  dealt  with  at  due 
length  in  subsequent  lectures. 
'^^  Having  proved  the  existence  and  importance 
of  mutations,  it  remains  to  inquire  how  far  the 
improvements  may  go  which  are  due  only  to 
fluctuating  variability.  As  the  term  indicates, 
this  variability  is  fluctuating  to  and  fro,  oscil- 
lating around  an  average  type.  It  never  fails 
nor  does  it,  under  ordinary  circumstances,  de- 
part far  from  the  fixed  average. 

But  the  deviation  may  be  enlarged  by  a  choice 
of  extremes.  In  sowing  their  seed,  the  aver- 
age of  the  strain  is  seen  to  be  changed,  and  in 
repeating  the  experiment  the  change  may  be 
considerable.  It  is  not  clear,  whether  theo- 
retically by  such  an  accumulation,  deviations 
might  be  reached  which  could  not  be  attained  at 
once  in  a  single  sowing.  This  question  is  hard- 
ly susceptible  of  an  experimental  answer,  as  it 
would  require  such  an  enormous  amount  of  seed 
from  a  few  mother  plants  as  can  scarcel}^  ever 
be  produced. 

The  whole  character  of  the  fluctuations  shows 
them  to  be  of  an  opposite  nature,  contrasting 


18  Descent 

manifestly  with  specific  and  varietal  characters. 
By  this  method  they  may  be  proved  to  be  in- 
adequate ever  to  make  a  single  step  along  the 
great  lines  of  evolution,  in  regard  to  progressive 
as  well  as  to  retrograde  development. 

First  of  all  fluctuations  are  linear,  amplify- 
ing  or  lessening  the  existing  qualities,  but  not 
really  changing  their  nature.  They  are  not 
observed  to  produce  anything  quite  new,  and 
evolution  of  course,  is  not  restricted  to  the  in- 
crease of  the  already  existing  peculiarities,  but 
depends  chiefly  on  the  continuous  addition  of 
new  characters  to  the  stock.  Fluctuations  al- 
ways oscillate  around  an  average,  and  if  re- 
moved from  this  for  some  time,  they  show  a 
tendency  to  return  to  it.  This  tendency,  called 
retrogression,  has  never  been  observed  to  fail, 
as  it  should,  in  order  to  free  the  new  strain  from 
the  links  with  the  average,  while  new  species 
and  new  varieties  are  seen  to  be  quite  free  from 
their  ancestors  and  not  linked  to  them  by 
intermediates. 

The  last  few  lectures  will  be  devoted  to  ques- 
tions concerning  the  great  problem  of  the  anal- 
ogy between  natural  and  artificial  selection. 
As  already  stated,  Darwin  made  this  analogy 
the  foundation  stone  of  his  theory  of  descent, 
and  he  met  with  the  severest  objections  and  crit- 
icisms precisely  on  this  point.     But  I  hope  to 


Theories  of  Evolution  19 

show  that  he  was  quite  right,  and  that  the 
cause  of  the  divergence  of  opinions  is  due 
simply  to  the  very  incomplete  state  of  knowl- 
edge concerning  both  processes.  If  both  are 
critically  analyzed  they  may  be  seen  to  comprise 
the  same  factors  and  further  discussion  may  be 
limited  to  the  appreciation  of  the  part,  which 
each  of  them  has  played  in  nature  and  among 
cultivated  plants. 

Both  natural  and  artificial  selection  are  part- 
ly specific,  and  partly  intra-specific  or  individ- 
ual. Nature  of  course,  and  intelligent  men  first 
chose  the  best  elementary  species  from  among 
the  swarms.  In  cultivation  this  is  the  process  of 
variety-testing.  In  nature  it  is  the  survival  of 
the  fittest  species,  or,  as  Morgan  designates  it, 
the  survival  of  species  in  the  struggle  for  ex- 
istence. The  species  are  not  changed  by  this 
struggle,  they  are  only  weighed  against  each 
other,  the  weak  being  thrown  aside. 

Within  the  chosen  elementary  species  there 
is  also  a  struggle.  It  is  obvious,  that  the  fluc- 
tuating variability  adapts  some  to  the  given 
circmnstances,  while  it  lessens  the  chances  of 
others.  A  choice  results,  and  this  choice  is 
what  is  often  exclusively  called  selection,  either 
natural  or  artificial.  In  cultivation  it  produces 
the  improved  and  the  local  races ;  in  nature  little 
is  known  about  improvement  in  this  way,  but 


20  Descent 

local  adaptations  with  slight  changes  of  the 
average  character  in  separate  localities,  seem 
to  be  of  quite  normal  occurrence. 

A  new  method  of  individual  selection  has 
been  used  in  recent  years  in  America,  especially 
by  W.  M.  Hays.  It  consists  in  judging  the 
hereditary  worth  of  a  plant  by  the  average  con- 
dition of  its  offspring,  instead  of  by  its  own 
visible  characters.  If  this  determination  of  the 
'^  centgener  power,"  as  Hays  calls  it,  should 
prove  to  be  the  true  principle  of  selection,  then 
indeed  the  analogy  between  natural  and  artifi- 
cial selection  would  lose  a  large  part  of  its  im- 
portance. We  will  reserve  this  question  for  the 
last  lecture,  as  it  pertains  more  to  the  future, 
than  to  our  present  stock  of  knowledge. 

Something  should  be  said  here  concerning 
hybrids  and  hybridism.  This  problem  has  of 
late  reached  such  large  proportions  that  it  can- 
not be  dealt  with  adequately  in  a  short  survey 
of  the  phenomena  of  heredity  in  general.  It 
requires  a  separate  treatment.  For  this  reason 
I  shall  limit  myself  to  a  single  phase  of  the  prob- 
lem, which  seems  to  be  indispensable  for  a  true 
and  at  the  same  time  easy  distinction  between 
elementary  species  and  retrograde  varieties.  Ac- 
cording to  accepted  terminology,  some  crosses 
are  to  be  considered  as  unsymmetrical,  while 
others  are  symmetrical.  The  first  are  one-sided, 


Theories  of  Evolution  21 

some  peculiarity  being  found  in  one  of  the 
parents  and  lacking  in  the  other.  The  second 
are  balanced,  as  all  the  characters  are  present 
in  both  parents,  but  are  found  in  a  different  con- 
dition. Active  in  one  of  them,  they  are  con- 
cealed or  inactive  in  the  other.  Hence  pairs  of 
contrasting  units  result,  while  in  unbalanced 
crosses  no  pairing  of  the  particular  character 
under  consideration  is  possible.  This  leads  to 
the  principal  difference  between  species  and  va- 
rieties, and  to  an  experimental  method  of  decid- 
ing between  them  in  difficult  and  doubtful  cases. 

Having  thus  indicated  the  general  outlines  of 
the  subjects  I  shall  deal  with,  something  now 
may  be  said  as  to  methods  of  investigation. 

There  are  two  points  in  which  scientific  in- 
vestigation differs  from  ordinary  pedigree-cul- 
ture in  practice.  First  the  isolation  of  the 
individuals  and  the  study  of  individual  inheri- 
tance, instead  of  averages.  Next  comes  the  task 
of  keeping  records.  Every  individual  must  be 
entered,  its  ancestry  must  be  known  as  com- 
pletely as  possible,  and  all  its  relations  must  be 
noted  in  such  a  form,  that  the  most  complete 
reference  is  always  possible.  Mutations  may 
come  unexpectedly,  and  when  once  arisen,  their 
parents  and  grand-parents  should  be  known. 
Records  must  be  available  which  will  allow  of 
a  most  complete  knowledge  of  the  whole  ances- 


22  Descent 

tral  line.  This,  and  approximately  this  only,  is 
the  essential  difference  between  experimental 
and  accidental  observation. 

Mutations  are  occurring  from  time  to  time  in 
the  wild  state  as  well  as  in  horticulture  and 
agriculture.  A  selection  of  the  most  interest- 
ing instances  will  be  given  later.  But  in  all 
such  cases  the  experimental  proof  is  wanting. 
The  observations  as  a  rule,  only  began  when  the 
mutation  had  made  its  appearance.  A  more  or 
less  vague  remembrance  about  the  previous 
state  of  the  plants  in  question  might  be  avail- 
able, though  even  this  is  generally  absent.  But 
on  doubtful  points,  concerning  possible  crosses 
or  possible  introduction  of  foreign  strains,  mere 
recollection  is  insufficient.  The  fact  of  the  mu- 
tation may  be  very  probable,  but  the  full  proof 
is,  of  course,  wanting.  Such  is  the  case  with 
the  mutative  origin  of  Xanthium  commune 
Wootoni  from  New  Mexico  and  of  Oenothera 
biennis  cruciata  from  Holland.  The  same 
doubt  exists  as  to  the  origin  of  the  Capsella 
heegeri  of  Solms-Laubach,  and  of  the  oldest 
recorded  mutation,  that  of  Chelidonium  lacinia- 
tum  in  Heidelberg  about  1600. 

First,  we  have  doubts  about  the  fact  itself. 
These,  however,  gradually  lose  their  impor- 
tance in  the  increasing  accumulation  of  evi- 
dence.    Secondly,  the  impossibility  of  a  closer 


Theories  of  Evolution  23 

inquiry  into  the  real  nature  of  the  change.  For 
experimental  purposes  a  single  mutation  does 
not  suffice;  it  must  be  studied  repeatedly,  and 
be  produced  more  or  less  arbitrarily,  according 
to  the  nature  of  the  problems  to  be  solved.  And 
in  order  to  do  this,  it  is  evidently  not  enough 
to  have  in  hand  the  mutated  individual,  but  it  is 
indispensable  to  have  also  the  mutable  parents, 
or  the  mutable  strain  from  which  it  sprang. 

All  conditions  previous  to  the  mutation  are  to 
be  considered  as  of  far  higher  importance  than 
all  those  subsequent  to  it. 

Now  mutations  come  unexpectedly,  and  if  the 
ancestry  of  an  accidental  mutation  is  to  be 
known,  it  is  of  course  necessary  to  keep  ac- 
counts of  all  the  strains  cultivated.  It  is  evi- 
dent that  the  required  knowledge  concerning  the 
ancestry  of  a  supposed  mutation,  must  neces- 
sarily nearly  all  be  acquired  from  the  plants  in 
the  experimental  garden. 

Obviously  this  rule  is  as  simple  in  theory,  as 
it  is  difficult  to  carry  out  in  practice.  First  of 
all  comes  the  book-keeping.  The  parents, 
grandparents  and  previous  ancestors  must  be 
known  individually.  Accounts  of  them  must  be 
kept  under  two  headings.  A  full  description  of 
their  individual  character  and  peculiarities 
must  always  be  available  on  the  one  hand,  and 
on  the  other,  all  facts  concerning  their  heredi- 


24  .  Descent 

tary  qualities.  These  are  to  be  deduced  from 
the  composition  of  the  progeny,  and  in  order 
to  obtain  complete  evidence  on  this  point,  two 
successive  generations  are  often  required.  The 
investigation  must  ascertain  the  average  condi- 
tion of  this  offspring  and  the  occurrence  of  any 
deviating  specimens,  and  for  both  purposes  it 
is  necessary  to  cultivate  them  in  relatively  large 
numbers.  It  is  obvious  that,  properly  speak- 
ing, the  whole  family  of  a  mutated  individual, 
including  all  its  nearer  and  more  remote  rela- 
tives, should  be  known  and  recorded. 

Hence  pedigree-book-keeping  must  become 
the  general  rule.  Subordinate  to  this  are  two 
further  points,  which  should  likewise  be  stated 
here.  One  pertains  to  the  pure  or  hybrid 
nature  of  the  original  strain,  and  the  other  to 
the  life-conditions  and  all  other  external  in- 
fluences. It  is  manifest  that  a  complete  under- 
standing of  a  mutation  depends  upon  full  infor- 
mation upon  these  points. 

All  experiments  must  have  a  beginning.  The 
starting-point  may  be  a  single  individual,  or  a 
small  group  of  plants,  or  a  lot  of  seeds.  In 
many  cases  the  whole  previous  history  is  ob- 
scure, but  sometimes  a  little  historical  evidence 
is  at  hand.  Often  it  is  evident  that  the  initial 
material  belongs  to  a  pure  species,  but  with  re- 
spect to  the  question  of  elementary  species  it  is 


fmrmrf  mutf 


Theories  of  Evolution  25 

not  rarely  open  to  doubt.  Large  numbers  of 
hybrid  plants  and  hybrid  races  are  in  existence, 
concerning  the  origin  of  which  it  is  impossible 
to  decide.  It  is  impossible  in  many  in- 
stances to  ascertain  whether  they  are  of 
hybrid  or  of  pure  origin.  Often  there  is  only 
one  way  of  determining  the  matter;  it  is  to 
guess  at  the  probable  parents  in  case  of  a  cross 
and  to  repeat  the  cross.  This  is  a  point  which 
always  requires  great  care  in  the  interpretation 
of  unusual  facts. 

Three  cases  are  to  be  distinguished  as  to 
heredity.  Many  plants  are  so  constituted  as  to 
be  fertilized  with  their  own  pollen.  In  this 
case  the  visits  of  insects  have  simply  to  be  ex- 
cluded, which  may  be  done  by  covering  plants 
with  iron  gauze  or  with  bags  of  prepared  paper. 
Sometimes  they  fertilize  themselves  without 
any  aid,  as  for  instance,  the  common  evening- 
primrose;  in  other  cases  the  pollen  has  to  be 
placed  on  the  stigma  artificially,  as  with  La- 
marck's evening-primrose  and  its  derivatives. 
Other  plants  need  cross-fertilization  in  order  to 
produce  a  normal  yield  of  seeds.  Here  two 
individuals  have  always  to  be  combined,  and 
the  pedigree  becomes  a  more  complicated  one. 
Such  is  the  case  with  the  toad-flax,  which  is 
nearly  sterile  with  its  own  pollen.  But  even  in 
these  cases  the  visits  of  insects  bringing  pollen 


26  Descent 

from  other  plants,  must  be  carefully  excluded. 
A  special  lecture  will  be  devoted  to  this  very  in- 
teresting source  of  impurity  and  of  uncertainty 
in  ordinary  cultures. 

Of  course,  crosses  may  lie  in  the  proposed 
line  of  work,  and  this  is  the  third  point  to  be 
alluded  to.  They  must  be  surrounded  with  the 
same  careful  isolation  and  protection  against 
bees,  as  any  other  fertilizations.  And  not  only 
the  seed-parent,  but  also  the  pollen  must  be 
kept  pure  from  all  possible  foreign  admixtures. 
A  pure  and  accurately  recorded  ancestry  is 
thus  to  be  considered  as  the  most  important 
condition  of  success  in  experimental  plant- 
breeding.  Next  to  this  comes  the  gathering  of 
the  seeds  of  each  individual  separately.  Fifty 
or  sixty,  and  often  more,  bags  of  seeds  are  by  no 
means  uncommon  for  a  single  experiment,  and 
in  ordinary  years  the  harvest  of  my  garden  is 
preserved  in  over  a  thousand  separate  lots. 

Complying  with  these  conditions,  the  origin 
of  species  may  be  seen  as  easily  as  any  other 
phenomenon.  It  is  only  necessary  to  have  a 
plant  in  a  mutable  condition.  Not  all  species 
are  in  such  a  state  at  present,  and  therefore  I 
have  begun  by  ascertaining  which  were  stable 
and  which  were  not.  These  attempts,  of  course, 
had  to  be  made  in  the  experimental  garden,  and 
large  quantities  of  seed  had  to  be  procured  and 


Theories  of  Evolution  27 

sown.  Cultivated  plants  of  course,  had  only 
a  small  chance  to  exhibit  new  qualities,  as  they 
have  been  so  strictly  controlled  during  so  many 
years.  Moreover  their  purity  of  origin  is  in 
many  cases  doubtful.  Among  wild  plants  only 
those  could  be  expected  to  reward  the  investi- 
gator which  were  of  easy  cultivation.  For  this 
reason  I  have  limited  myself  to  the  trial  of  wild 
plants  of  Holland,  and  have  had  the  good  for- 
tune to  find  among  them  at  least  one  species  in  a 
state  of  mutability.  It  was  not  really  a  native 
plant,  but  one  that  had  been  introduced  from 
America  and  belongs  to  an  American  genus.  I 
refer  to  the  great  evening-primrose  or  the  even- 
ing-primrose of  Lamarck.  A  strain  of  this 
beautiful  species  is  growing  in  an  abandoned 
field  in  the  vicinity  of  Hilversum,  at  a  short  dis- 
tance from  Amsterdam.  Here  it  has  escaped 
from  a  park  and  multiplied.  In  doing  so  it  has 
produced  and  is  still  producing  quite  a  number 
of  new  types,  some  of  which  may  be  considered 
as  retrograde  varieties,  while  others  evidently 
are  of  the  nature  of  progressive  elementary 
species. 

This  interesting  plant  has  afforded  me  the 
means  of  observing  directly  how  new  species 
originate,  and  of  studying  the  laws  of  these 
changes.  My  researches  have  followed  a  double 
line  of  inquiry.     On  one  side,  I  have  limited 


28  Descent 

myself  to  direct  field  observations,  and  to  tests 
of  seed,  collected  from  the  wild  plants  in  their 
native  locality.  Obviously  the  mutations  are 
decided  within  the  seed,  and  the  culture  of 
young  plants  from  them  had  no  other  aim  than 
that  of  ascertaining  what  had  occurred  in  the 
field.  x\nd  then  the  many  chances  of  destruc- 
tion that  threaten  young  plants  in  a  wild  state, 
could  be  avoided  in  the  garden,  where  enviro- 
mental  factors  can  be  controlled. 

My  second  line  of  inquiry  was  an  experi- 
mental repetition  of  the  phenomena  which  were 
only  partly  discerned  at  the  native  locality.  It 
was  not  my  aim  to  intrude  into  the  process,  nor 
to  try  to  bring  out  new  features.  My  only  ob- 
ject was  to  submit  to  the  precepts  just  given 
concerning  pure  treatment,  individual  seed- 
gathering,  exclusion  of  crosses  and  accurate 
recording  of  all  the  facts.  The  result  has  been 
a  pedigree  which  now  permits  of  stating  the  re- 
lation between  all  the  descendants  of  my  orig- 
inal introduced  plant.  This  pedigree  at  once 
exhibits  the  laws  followed  by  the  mutating  spe- 
cies. The  main  fact  is,  that  it  does  not  change 
itself  gradually,  but  remains  unaffected  during 
all  succeeding  generations.  It  only  throws  off 
new  forms,  which  are  sharply  contrasted  with 
the  parent,  and  which  are  from  the  very  begin- 
ning as  perfect  and  as  constant,  as  narrowly 


Theories  of  Evolution  29 

defined  and  as  pure  of  type  as  might  be  ex- 
j)ected  of  any  species. 

These  new  species  are  not  produced  once  or 
in  single  individuals,  but  yearly  and  in  large 
numbers.  The  whole  phenomenon  conveys  the 
idea  of  a  close  group  of  mutations,  all  belonging 
to  one  single  condition  of  mutability.  Of  course 
this  mutable  state  must  have  had  a  beginning, 
as  it  must  sometime  come  to  an  end.  It  is  to 
be  considered  as  a  period  within  the  life-time  of 
the  species  and  probably  it  is  only  a  small  part 
of  it. 

The  detailed  description  of  this  experiment, 
however,  I  must  delay  to  a  subsequent  lecture, 
but  I  may  be  allowed  to  state,  that  the  discov- 
ery of  this  period  of  mutability  is  of  a  definite 
theoretical  importance.  "  One  of  the  greatest  ob- 
jections to  the  Darwinian  theory  of  descent 
arose  from  the  length  of  time  it  would  require, 
if  all  evolution  was  to  be  explained  on  the 
theory  of  slow  and  nearly  invisible  changes. 
This  difficulty  is  at  once  met  and  fully  sur- 
mounted by  the  hypothesis  of  periodical  but 
sudden  and  quite  noticeable  steps.  This  as- 
sumption requires  only  a  limited  number  of 
mutative  periods,  which  might  well  occur  within 
the  time  allowed  by  physicists  and  geologists 
for  the  existence  of  animal  and  vegetable  life 
on  the  earth. 


30  Descent 

Smnming  up  the  main  points  of  these  intro- 
ductory remarks,  I  propose  to  deal  with  the  sub- 
jects mentioned  above  at  some  length,  devoting 
to  each  of  them,  if  possible  at  least  an  entire 
lecture.  The  decisive  facts  and  discussions 
upon  which  the  conclusions  are  based  will  be 
given  in  every  case.  Likewise  I  hope  to  point 
out  the  weak  places  and  the  lacunae  in  our  pres- 
ent knowledge,  and  to  show  the  way  in  which 
each  of  you  may  try  to  contribute  his  part  to- 
wards the  advancement  of  science  in  this  sub- 
ject. Lastly  I  shall  try  to  prove  that  sudden 
mutation  is  the  normal  way  in  which  nature 
produces  new  species  and  new  varieties.  These 
mutations  are  more  readily  accessible  to  ob- 
servation and  experiment  than  the  slow  and 
gradual  changes  surmised  by  Wallace  and  his 
followers,  which  are  entirely  beyond  our  pres- 
ent and  future  experience. 
\  The  theory  of  mutations  is  a  starting-point 
for  direct  investigation,  while  the  general  belief 
in  slow  changes  has  held  back  science  from  such 
investigations  during  half  a  century. 

Coming  now  to  the  subdivisions  and  headings 
under  which  my  material  is  to  be  presented,  I 
propose  describing  first  the  real  nature  of  the 
elementary  species  and  retrograde  varieties, 
both  in  normal  form  and  in  hybridizations.  A 
discussion  of  other  types  of  varieties,  includ- 


Theories  of  Evolution  31 

ing  monstrosities  will  complete  the  general  plan. 
The  second  subdivision  will  deal  with  the  origin 
of  species  and  varieties  as  taught  by  experiment 
and  observation,  treating  separately  the  sud- 
den variations  which  to  my  mind  do  produce 
new  forms,  and  subsequently  the  fluctuations 
which  I  hold  to  be  not  adequate  to  this  purpose. 


B.    ELEMENTARY  SPECIES 
Lecture  II 

ELEMENTARY   SPECIES   IN   NATURE 

What  are  species?  Species  are  considered 
as  the  true  units  of  nature  by  the  vast  majority 
of  biologists.  They  have  gained  this  high 
rank  in  our  estimation  principally  through  the 
influence  of  Linnaeus.  They  have  supplanted 
the  genera  which  were  the  accepted  units  before 
Linnaeus.  They  are  now  to  be  replaced  in  their 
turn,  by  smaller  types,  for  reasons  which  do  not 
rest  upon  comparative  studies  but  upon  direct 
experimental  evidence. 

Biological  studies  and  practical  interests 
alike  make  new  demands  upon  systematic  bot- 
any. Species  are  not  only  the  subject-material 
of  herbaria  and  collections,  but  they  are  living 
entities,  and  their  life-history  and  life-condi- 
tions command  a  gradually  increasing  interest. 
One  phase  of  the  question  is  to  determine  the 
easiest  manner  to  deal  with  the  collected  forms 
of  a  country,  and  another  feature  is  the  problem 

32 


Elementary  Species  in  Nature  33 

as  to  what  groups  are  real  units  and  will  remain 
constant  and  unchanged  through  all  the  years 
of  our  observations. 

Before  Linnaeus,  the  genera  were  the  real 
units  of  the  system.  De  Candolle  pointed  out 
that  the  old  common  names  of  plants,  such  as 
roses  and  clover,  poplars  and  oaks,  nearly  all 
refer  to  genera.  The  type  of  the  clovers  is 
rich  in  color,  and  the  shape  of  the  flower-heads 
and  the  single  flowers  escape  ordinary  obser- 
vation; but  notwithstanding  this,  clovers  are 
easily  recognized,  even  if  new  types  come  to 
hand.  White  and  red  clovers  and  many  other 
species  are  distinguished  simply  by  adjectives, 
the  generic  name  remaining  the  same  for  all. 

Tournefort,  who  lived  in  the  second  half  of 
the  17th  century  (1656-1708),  is  generally  con- 
sidered as  the  author  of  genera  in  systematic 
botany.  He  adopted,  what  was  at  that  time 
the  general  conception  and  applied  it  through- 
out the  vegetable  kingdom.  He  grouped  the 
new  and  the  rare  and  the  previously  over- 
looked forms  in  the  same  manner  in  which  the 
more  conspicuous  plants  were  already  ar- 
ranged by  universal  consent.  Species  were  dis- 
tinguished by  minor  marks  and  often  indicated 
by  short  descriptions,  but  they  were  consid- 
ered of  secondary  importance. 

Based  on  the  idea  of  a  direct  creation  of  all 


34  Elementary  Species 

living  beings,  the  genera  were  then  accepted  as 
the  created  forms.  They  were  therefore  re-  • 
garded  as  the  real  existing  types,  and  it  was 
generally  surmised  that  species  and  varieties 
owed  their  origin  to  subsequent  changes  under 
the  influence  of  external  conditions.  Even  Lin- 
naeus agreed  with  this  view  in  his  first  treatises 
and  in  his  '^Philosophical  Botany"  he  still  kept 
to  the  idea  that  all  genera  had  been  created  at 
once  with  the  beginning  of  life. 

Afterwards  Linnaeus  changed  his  opinion  on 
this  important  point,  and  adopted  species  as  the 
units  of  the  svstem.  He  declared  them  to  be 
the  created  forms,  and  by  this  decree,  at  once  re- 
duced the  genera  to  the  rank  of  artificial  groups. 
Linnaeus  was  well  aware  that  this  conception 
was  wholly  arbitrary,  and  that  even  the  species 
are  not  real  indivisible  entities.  But  he  sim- 
ply forbade  the  study  of  lesser  subdivisions. 
At  his  time  he  was  quite  justified  in  doing  so, 
because  the  first  task  of  the  systematic  botanists 
was  the  clearing  up  of  the  chaos  of  forms  and 
the  bringing  of  them  into  connection  with  their 
real  allies. 

Linnaeus  himself  designated  the  subdivisions 
of  the  species  as  varieties,  but  in  doing  so  he 
followed  two  clearly  distinct  principles.  In 
some  cases  his  species  were  real  plants,  and  the 
varieties  seemed  to  be  derived  from  them  by 


Elementary  Species  in  Nature  35 

some  simple  changes.  They  were  subordinated 
to  the  parent-species.  In  other  cases  his  spe- 
cies were  groups  of  lesser  forms  of  equal  value, 
and  it  was  not  possible  to  discern  which  was 
the  primary  and  which  were  the  derivatives. 

These  two  methods  of  subdivision  seem  in  the 
main,  and  notwithstanding  their  relatively  im- 
perfect application  in  many  single  examples,  to 
correspond  with  two  really  distinct  cases.  The 
derivative  varieties  are  distinguished  from  the 
parent-species  by  some  single,  but  striking  mark, 
and  often  this  attribute  manifests  itself  as  the 
loss  of  some  apparent  quality.  The  loss  of 
spines  and  of  hairs  and  the  loss  of  blue  and  red 
flower-colors  are  the  most  notorious,  but  in 
rarer  cases  many  single  peculiarities  may  dis- 
appear, thereby  constituting  a  variety.  This 
relation  of  varieties  to  the  parent-species  is 
gradually  increasing  in  importance  in  the  esti- 
mation of  botanists,  sharply  contrasting  with 
those  cases,  in  which  such  dependency  is  not  to 
be  met  with. 

If  among  the  subdivisions  of  a  species,  no 
single  one  can  be  pointed  out  as  playing  a  pri- 
mary part,  and  the  others  can  not  be  traced 
back  to  it,  the  relation  between  these  lesser 
units  is  of  course  of  another  character.  They 
are  to  be  considered  of  equal  importance.  They 
are  distinguished  from  each  other  by  more  than 


36  Elementary  Species 

one  character,  often  by  slight  differences  in 
nearly  all  their  organs  and  qualities.  Such 
forms  have  come  to  be  designated  as  "  elemen- 
tary species."  They  are  only  varieties  in  a 
broad  and  vague  systematic  significance  of  the 
word,  not  in  the  sense  accorded  to  this  term  in 
horticultural  usage,  nor  in  a  sharper  and  more 
scientific  conception. 

Genera  and  species  are,  at  the  present  time, 
for  a  large  part  artificial,  or  stated  more  cor- 
rectly, conventional  groups.  Every  systematist 
is  free  to  delimit  them  in  a  wider  or  in  a  nar- 
rower sense,  according  to  his  judgment.  The 
greater  authorities  have  as  a  rule  preferred 
larger  genera,  others  of  late  have  elevated  in- 
numerable subgenera  to  the  rank  of  genera. 
This  would  work  no  real  harm,  if  unfortu- 
nately, the  names  of  the  plants  had  not  to  be 
changed  ea>ch  time,  according  to  current  ideas 
concerning  genera.  Quite  the  same  inconstancy 
is  observed  with  species.  In  the  Handbook 
of  the  British  Flora,  Bentham  and  Hooker  de- 
scribe the  forms  of  brambles  under  5  species, 
while  Babington  in  his  Manual  of  British 
Botany  makes  45  species  out  of  the  same  mate- 
rial. So  also  in  other  cases.  For  instance,  the 
willows  which  have  13  species  in  one  and  31 
species  in  the  other  of  these  manuals,  and  the 
hawkweeds  for  which  the  figures  are  7  and  32 


Elementary  Species  in  Nature  37 

respectively.  Other  authors  have  made  still 
greater  numbers  of  species  in  the  same  groups. 

It  is  very  difficult  to  estimate  systematic  dif- 
ferences on  the  ground  of  comparative  studies 
alone.  All  sorts  of  variability  occur,  and  no 
individual  or  small  group  of  specimens  can 
really  be  considered  as  a  reliable  representa- 
tive of  the  supposed  type.  Many  original  diag- 
noses of  new  species  have  been  founded  on  di- 
vergent specimens  and  of  course,  the  type  can 
afterwards  neither  be  derived  from  this  indi- 
vidual, nor  from  the  diagnosis  given. 

This  chaotic  state  of  things  has  brought  some 
botanists  to  the  conviction  that  even  in  syste- 
matic studies  only  direct  experimental  evidence 
can  be  relied  upon.  This  conception  has  in- 
duced them  to  test  the  constancy  of  species  and 
varieties,  and  to  admit  as  real  units  only  such 
groups  of  individuals  as  prove  to  be  uniform 
and  constant  throughout  succeeding  gener- 
ations. The  late  Alexis  Jordan,  of  Lyons  in 
France,  made  extensive  cultures  in  this  direc- 
tion. In  doing  so,  he  discovered  that  syste- 
matic species,  as  a  rule,  comprise  some  lesser 
forms,  which  often  cannot  easily  be  distin- 
guished when  grown  in  different  regions,  or  by 
comparing  dried  material.  This  fact  was,  of 
course,  most  distasteful  to  the  systematists  of 
his  time  and  even  for  a  long  period  afterwards 


38  Elementary  Species 

tliey  attempted  to  discredit  it.  Milde  and  many 
others  have  opposed  these  new  ideas  with  some 
temporary  success.  Only  of  late  has  the  school 
of  Jordan  received  due  recognition,  after 
Thuret,  de  Bary,  Rosen  and  others  tested 
its  practices  and  openly  pronounced  for  them. 
Of  late  Wittrock  of  Sweden  has  joined  them, 
making  extensive  experimental  studies  concern- 
ing the  real  units  of  some  of  the  larger  species 
of  his  country. 

From  the  evidence  given  by  these  eminent 
authorities,  we  may  conclude  that  systematic 
species,  as  they  are  accepted  nowadays,  are  as 
a  rule  compound  groups.  Sometimes  they  con- 
sist of  two  or  three,  or  a  few  elementary  types, 
but  in  other  cases  they  comprise  twenty,  or  fifty, 
or  even  hundreds  of  constant  and  well  differen- 
tiated forms. 

The  inner  constitution  of  these  groups  is 
however,  not  at  all  the  same  in  all  cases.  This 
will  be  seen  by  the  description  of  some  of  the 
more  interesting  of  them.  The  European 
heartsease,  from  which  our  garden-pansies  have 
been  chiefly  derived,  will  serve  as  an  example. 
The  garden-pansies  are  a  hybrid  race,  won  by 
crossing  the  Viola  tricolor  with  the  large  flow- 
ered and  bright  yellow  V.  lutea.  They  com- 
bine, as  everyone  knows,  in  their  wide  range  of 


Elementary  Species  in  Nature  39 

varieties,  the  attributes  of  the  latter  with  the 
peculiarities  of  the  former  species. 

Besides  the  liitea,  there  are  some  other  spe- 
cies, nearly  allied  to  tricolor,  as  for  instance, 
cornuta,  calcarata,  and  altaica,  which  are  com- 
bined with  it  under  the  head  of  Melanium  as  a 
subgenus,  and  which  together  constitute  a  syste- 
matic unity  of  undoubted  value,  but  ranging  be- 
tween the  common  conceptions  of  genus  and 
species.  These  forms  are  so  nearly  allied  to 
the  heartsease  that  they  have  of  late  been  made 
use  of  in  crosses,  in  order  to  widen  the  range 
of  variability  of  garden-pansies. 

Viola  tricolor  is  a  common  European  weed. 
It  is  widely  dispersed  and  very  abundant,  grow- 
ing in  many  localities  in  large  numbers.  It  is 
an  annual  and  ripens  its  seeds  freely,  and  if  op- 
portunity is  afforded,  it  multiplies  rapidly. 

Viola  tricolor  has  three  subspecies,  which 
have  been  elevated  to  the  rank  of  species  by 
some  authors,  and  which  may  here  be  called,  for 
brevity's  sake,  by  their  binary  names.  One  is 
the  typical  V.  tricolor,  with  broad  flowers,  vari- 
ously colored  and  veined  with  yellow,  purple 
and  white.  It  occurs  in  waste  places  on  sandy 
soil.  The  second  is  called  V.  arvensis  or  the 
field-pansy;  it  has  small  inconspicuous  flowers, 
with  pale  yellowish  petals  which  are  shorter 
than  the  sepals.     It  pollinates  itself  without  the 


40  Elementary  Species 

aid  of  insects,  and  is  widely  dispersed  in  culti- 
vated fields.  The  third  form,  F.  alpestris, 
grows  in  the  Alps,  but  is  of  lesser  importance 
for  our  present  discussion. 

Anywhere  throughout  the  central  part  of 
Euroi)e  V.  tricolor  and  V.  arvensis  may  be  seen, 
each  occupying  its  own  locality.  They  may  be 
considered  as  ranging  among  the  most  common 
native  plants  of  the  particular  regions  they  in- 
habit. They  vary  in  the  color  of  the  flowers, 
branching  of  the  stems,  in  the  foliage  and  other 
parts,  but  not  to  such  an  extent  as  to  consti- 
tute distinct  strains.  They  have  been  brought 
into  cultivation  by  Jordan,  Wittrock  and  others, 
but  throughout  Europe  each  of  them  constitutes 
a  single  type. 

These  types  must  be  very  old  and  constant, 
fluctuating  always  within  the  same  distinct  and 
narrow  limits.  No  slow,  gradual  changes  can 
have  taken  place.  In  different  countries  their 
various  habitats  are  as  old  as  the  historical 
records,  and  probably  many  centuries  older. 
They  are  quite  independent  of  one  another,  the 
distance  being  in  numerous  cases  far  too  great 
for  the  exchange  of  pollen  or  of  seeds.  If  slow 
and  gradual  changes  were  the  rule,  the  types 
could  not  have  remained  so  uniform  throughout 
the  whole  range  of  these  two  species.  They 
would  necessarily  have  split  up  into  thousands 


Elementary  Species  in  Nature  41 

and  thousands  of  minor  races,  which  would 
show  their  peculiar  characteristics  if  tested  by 
cultures  in  adjacent  beds.  This  however,  is  not 
what  happens.  As  a  matter  of  fact  F.  tricolor 
and  V,  arvensis  are  widely  distributed  but 
wholly  constant  types. 

Besides  these,  there  occur  distinct  types  in 
numerous  localities.  Some  of  them  evidently 
have  had  time  and  opportunity  to  spread  more 
or  less  widely  and  now  occupy  larger  regions  or 
even  whole  countries.  Others  are  narrowly  lim- 
ited, being  restricted  to  a  single  locality.  Witt- 
rock  collected  seeds  or  plants  from  as  many 
localities  as  possible  in  different  parts  of 
Sweden  and  neighboring  states  and  sowed  them 
in  his  garden  near  Stockholm.  He  secured 
seeds  from  his  plants,  and  grew  from  them  a 
second,  and  in  many  cases  a  third  generation  in 
order  to  estimate  the  amount  of  variability.  As 
a  rule  the  forms  introduced  into  his  garden 
proved  constant,  notwithstanding  the  new  and 
abnormal  conditions  under  which  they  were 
propagated. 

First  of  all  we  may  mention  three  perennial 
forms  called  by  him  Viola  tricolor  ammotropha, 
V.  tricolor  coniophila  and  V.  stenochila.  The 
typical  F.  tricolor  is  an  annual  plant,  sowing 
itself  in  summer  and  germinating  soon  after- 
wards.    The  young  plants  thrive  throughout 


42  Elementary  Species 

the  latter  part  of  the  summer  and  during  the 
fall,  reaching  an  advanced  stage  of  development 
of  the  branched  stems  before  winter.  Early  in 
the  spring  the  flowers  begin  to  open,  but  after 
the  ripening  of  the  seeds  the  whole  plant  dies. 

The  three  perennial  species  just  mentioned 
develop  in  the  same  manner  in  the  first  year. 
During  their  flowering  period,  however,  and 
afterwards,  they  produce  new  shoots  from  the 
lower  parts  of  the  stem.  They  prefer  dry  and 
sandy  soils,  often  becoming  covered  with  the 
sand  that  is  blown  on  them  by  the  winds.  They 
are  prepared  for  such  seemingly  adverse  cir- 
cumstances by  the  accumulation  of  food  in  the 
older  stems  and  by  the  capacity  of  the  new 
shoots  to  thrive  on  this  food  till  they  have 
become  long  enough  to  reach  the  light.  V. 
tricolor  ammotropha  is  native  near  Ystad 
in  Sweden,  and  the  other  two  forms  on  Got- 
land. All  three  have  narrowly  limited  habi- 
tats. 

The  typical  tricolored  heartsease  has  re- 
mained annual  in  all  its  other  subspecies.  It 
may  be  divided  into  two  types  in  the  first  place : 
V.  tricolor  genuina  and  F.  tricolor  versicolor. 
Both  of  them  have  a  wide  distribution  and  seem 
to  be  the  prototypes  from  which  the  rarer  forms 
must  have  been  derived.  Among  these  latter 
Wittrock   describes    seven   local   types,   which 


Elementary  Species  in  Nature  43 

proved  to  be  constant  in  his  pedigree-cultures. 
Some  of  them  have  produced  other  forms,  re- 
lated to  them  in  the  way  of  varieties.  They  all 
have  nearly  the  same  general  habit  and  do  not 
exhibit  any  marked  differences  in  their  growth, 
in  the  structure  and  branching  of  the  stems,  or 
in  the  character  of  their  foliage.  Differentiat- 
ing points  are  to  be  found  mainly  in  the  colors 
and  patterns  of  the  flowers.  The  veins,  which 
radiate  from  the  centre  of  the  corolla  are 
branched  in  some  and  undivided  in  others;  in 
one  elementary  species  they  are  wholly  lack- 
ing. The  purple  color  may  be  absent,  leav- 
ing the  flowers  of  a  pale  or  a  deep  yellow.  Or 
the  purple  may  be  reddish  or  bluish.  Of 
the  petals  all  five  may  have  the  purple  hue 
on  their  tips,  or  this  attribute  may  be  limited  to 
the  two  upper  ones.  Contrasting  with  this  wide 
variability  is  the  stability  of  the  yellow  spot  in 
the  centre,  which  is  always  present  and  becomes 
inconspicuous  only,  when  the  whole  petals  are 
of  the  same  hue.  It  is  a  general  conception 
that  colors  and  color-markings  are  liable  to 
great  variability  and  do  not  constitute  reliable 
standards.  But  the  cultures  of  Wittrock  have 
proved  the  contrary,  at  least  in  the  case  of  the 
violets.  No  pattern,  however  quaint,  appears 
changeable,  if  one  elementary  species  only  is 
considered.     Hundreds   of  plants   from   seeds 


44  Elementary  Species 

from  one  localitj^  may  be  grown,  and  all  will  ex- 
hibit exactly  the  same  markings.  Most  of  these 
forms  are  of  very  local  occurrence.  The  most 
beautiful  of  all,  the  ornatissinia,  is  found  only  in 
Jemtland,  the  aurohadia  only  in  Sodermanland, 
the  anopetala  in  other  localities  in  the  same 
countr}^  the  roseola  near  Stockholm,  and  the 
yellow  lutescens  in  Finmarken. 

The  researches  of  Wittrock  included  only  a 
small  number  of  elementary  species,  but  every 
one  who  has  observed  the  violets  in  the  central 
parts  of  Europe  must  be  convinced  that  many 
dozens  of  constant  forms  of  the  typical  Viola 
tricolor  might  easily  be  found  and  isolated. 

We  now  come  to  the  field  pansy,  the  Viola  ar- 
vensisj  a  very  common  weed  in  the  grain-fields 
of  central  Europe.  I  have  already  mentioned 
its  small  corolla,  surpassed  by  the  lobes  of  the 
cal}rx  and  its  capacity  of  self-fertilization.  It 
has  still  other  curious  differentiating  charac- 
ters; the  pollen  grains,  which  are  square  in 
V.  tricolor,  are  five-sided  in  V.  arvensis. 
Some  transgressive  fluctuating  variability  may 
occur  in  both  cases  through  the  admixture 
of  pollen-grains.  Even  three-angled  pollen- 
grains  are  seen  sometimes.  Other  marks  are 
observed  in  the  form  of  the  anthers  and  the 
spur. 

There  seem  to  be  very  many  local  subspecies 


Elementary  Species  in  Nature  45 

of  the  field-pansy.  Jordan  has  described  some 
from  tlie  vicinity  of  Lyons,  and  Wittrock  others 
from  the  northern  parts  of  Europe.  They 
diverge  from  their  common  prototype  in  nearly 
all  attributes,  the  flowers  not  showing  the 
essential  differ entiating  characters  as  in  the 
F.  tricolor.  Some  have  their  flower-stalks 
erect,  and  in  others  the  flowers  are  held  nearly 
at  right  angles  to  the  stem.  F.  pallescens  is  a 
small,  almost  unbranched  species  with  small 
pale  flowers.  F.  segetalis  is  a  stouter  species 
with  two  dark  blue  spots  on  the  tips  of  the  upper 
petals.  F.  agrestis  is  a  tall  and  branched, 
hairy  form.  F.  nemausensis  attains  a  height  of 
only  10  cm.,  has  rounded  leaves  and  long 
flower-stalks.  Even  the  seeds  afford  charac- 
ters which  may  be  made  use  of  in  isolating  the 
various  species. 

The  above-mentioned  elementary  forms  be- 
long to  the  flora  of  southern  France,  and  Witt- 
rock  has  isolated  and  cultivated  a  number  of 
others  from  the  fields  of  Sweden.  A  species 
from  Stockholm  is  called  Viola  patens;  V.  arven- 
sis  curtisepala  occurs  in  Gotland,  and  F.  aw  en- 
sis  striolata  is  a  distinct  form,  which  has  ap- 
peared in  his  cultures  without  its  true  origin 
being  ascertained. 

The  alpine  violets  comprise  a  more  wide- 
spread type  with  some  local  elementary  species 


46  Elementary  Species 

derived  exactly  in  the  same  way  as  the  tricol- 
ored  field-pansies. 

Summarizing  the  general  result  of  this  de- 
scription we  see  that  the  original  species  Viola 
tricolor  may  be  split  up  into  larger  and  lesser 
groups  of  separate  forms.  These  last  prove  to 
be  constant  in  pedigree-cultures,  and  therefore 
are  to  be  considered  as  really  existent  units. 
They  are  very  numerous,  comprising  many 
dozens  in  each  of  the  two  larger  subdivisions. 

All  systematic  grouping  of  these  forms,  and 
their  combination  into  subspecies  and  species 
rests  on  the  comparative  study  of  their  charac- 
ters. The  result  of  such  studies  must  neces- 
sarily depend  on  principles  which  underlie 
them.  According  to  the  choice  of  these 
principles,  the  construction  of  the  groups 
will  be  found  to  be  different.  Wittrock  trusts 
in  the  first  place  to  morphologic  charac- 
ters, and  considers  the  development  as  passing 
from  the  more  simple  to  the  more  complex 
types.  On  the  other  hand  the  geographic  dis- 
tribution may  be  considered  as  an  indication  of 
the  direction  of  evolution,  the  wide-spread 
forms  being  regarded  as  the  common  parents  of 
the  minor  local  species. 

However,  such  considerations  are  only  of  sec- 
ondary importance.  It  must  be  borne  in  mind 
that  an  ordinary  systematic  species  may  include 


Elementary  Species  in  Nature  47 

many  dozens  of  elementary  forms,  each  of  which 
remains  constant  and  unchanged  in  successive 
generations,  even  if  cultivated  in  the  same  gar- 
den and  under  similar  external  conditions. 

Leaving  the  violets,  we  may  take  the  vernal 
whitlow-grass  or  Draba  verna  for  a  second  illus- 
tration. This  little  annual  cruciferous  plant  is 
common  in  the  fields  of  many  parts  of  the 
United  States,  though  originally  introduced 
from  Europe.  It  has  small  basal  rosettes  which 
develop  during  summer  and  winter,  and  pro- 
duce numerous  leafless  flowering  stems  early  in 
the  spring.  It  is  a  native  of  central  Europe 
and  western  Asia,  and  mav  be  considered  as  one 
of  the  most  common  plants,  occurring  anywhere 
in  immense  numbers  on  sandy  soils.  Jordan 
was  the  first  to  point  out  that  it  is  not  the  same 
throughout  its  entire  range.  Although  a  hasty 
survey  does  not  reveal  differences,  they  show 
themselves  on  closer  inspection.  De  Bary, 
Thuret,  Eosen  and  many  others  confirmed  this 
result,  and  repeated  the  pedigree-cultures  of 
Jordan.  Every  type  is  constant  and  remains 
unchanged  in  successive  generations.  The  an- 
thers open  in  the  flower-buds  and  pollinate  the 
stigmas  before  the  expansion  of  the  flowers, 
thus  assuring  self-fertilization.  Moreover, 
these  inconspicuous  little  flowers  are  only  spar- 
ingly visited  by  insects.     Dozens  of  subspecies 


48  Elementary  Species 

may  be  cultivated  in  the  same  garden  without 
any  real  danger  of  their  intercrossing.  They 
remain  as  pure  as  under  perfect  isolation. 

It  is  very  interesting  to  observe  the  aspect  of 
such  tyiDes,  when  growing  near  each  other. 
Hundreds  of  rosettes  exhibit  one  type,  and  are 
undoubtedly  similar.  The  alternative  group  is 
distinguishable  at  first  sight,  though  the  differ- 
entiating marks  are  often  so  slight  as  to  be 
traceable  with  difficulty.  Two  elementary  spe- 
cies occur  in  Holland,  one  with  narrow  leaves  in 
the  western  provinces  and  one  with  broader 
foliage  in  the  northern  parts.  I  have  cultivated 
them  side  by  side,  and  was  as  much  struck  with 
the  uniformity  within  each  group,  as  with  the 
contrast  between  the  two  sets. 

Nearly  all  organs  show  differences.  The 
most  marked  are  those  of  the  leaves,  which  may 
be  small  or  large,  linear  or  elliptic  or  oblong  and 
even  rhomboidal  in  shape,  more  or  less  hairy 
with  simple  or  with  stellate  branched  hairs,  and 
finally  of  a  pure  green  or  of  a  glaucous  color. 
The  petals  are  as  a  rule  obcordate,  but  this  type 
may  be  combined  with  others  having  more  or 
less  broad  emarginations  at  the  summit,  and 
with  differences  in  breadth  which  varv  from  al- 
most  linear  types  to  others  which  touch  along 
their  margins.  The  pods  are  short  and  broad, 
or  long  and  narrow,  or  varying  in  sundry  other 


J 


Elementary  Species  in  Nature  49 

ways.  All  in  all  there  are  constant  differences 
which  are  so  great  that  it  has  been  possible  to 
distinguish  and  to  describe  large  numbers  of 
types. 

Many  of  them  have  been  tested  as  to  their 
constancy  from  seed.  Jordan  made  numerous 
cultures,  some  of  which  lasted  ten  or  twelve 
years;  Thuret  has  verified  the  assertion  con- 
cerning their  constancy  by  cultures  extending 
over  seven  years  in  some  instances ;  Villars  and 
de  Bary  made  numerous  trials  of  shorter  dura- 
tion. All  agree  as  to  the  main  points.  The  local 
races  are  uniform  and  come  true  from  seed ;  the 
variability  of  the  species  is  not  of  a  fluctuating, 
but  of  a  polymorphous  nature.  A  given  ele- 
mentary species  keeps  within  its  limits  and  can- 
not vary  beyond  them,  but  the  whole  group 
gives  the  impression  of  variability  by  its  wide 
range  of  distinct,  but  nearly  allied  forms. 

The  geographic  distribution  of  these  ele- 
mentary species  of  the  whitlow-grass  is  quite 
distinct  from  that  of  the  violets.  Here  predom- 
inant species  are  limited  to  restricted  locali- 
ties. Most  of  them  occupy  one  or  more  depart- 
ments of  France,  and  in  Holland  two  of  them 
are  spread  over  several  provinces.  An  import- 
ant number  are  native  in  the  centre  of  Europe, 
and  from  the  vicinity  of  Lyons,  Jordan  suc- 
ceeded in  establishing  about  fifty  elementary 


50  Elementary  Species 

species  in  his  garden.  In  this  region  they  are 
crowded  together  and  not  rarely  two  or  even 
more  quite  distinct  forms  are  observed  to  grow 
side  by  side  on  the  same  spot.  Farther  away 
from  this  center  they  are  more  widely  dispersed, 
each  holding  its  own  in  its  habitat.  In  all,  Jor- 
dan has  distinguished  about  two  hundred  spe- 
cies of  Draha  verna  from  Europe  and  western 
Asia.  Subsequent  authors  have  added  new 
types  to  the  already  existing  number  from  time 
to  time. 

The  constancy  of  these  elementary  species  is 
directly  proven  by  the  experiments  quoted 
above,  and  moreover  it  may  be  deduced  from  the 
uniformity  of  each  type  within  its  own  domain. 
These  are  so  large  that  most  of  the  localities  are 
practically  isolated  from  one  another,  and  must 
have  been  so  for  centuries.  If  the  types  were 
slowly  changing  such  localities  would  often, 
though  of  course  not  always,  exhibit  slighter 
differences,  and  on  the  geographic  limits  of 
neighboring  species  intermediates  would  be 
found.  Such  however,  are  not  on  record. 
Hence  the  elementary  species  must  be  regarded 
as  old  and  constant  types. 

The  question  naturally  arises  how  these 
groups  of  nearly  allied  forms  may  originally 
have  been  produced.  Granting  a  common  ori- 
gin for  all  of  them,  the  changes  may  have  been 


Elementary  Species  in  Nature  51 

simultaneous  or  successive.  According  to  the 
geographic  distribution,  the  place  of  common 
origin  must  probably  be  sought  in  the  southern 
part  of  central  Europe,  perhaps  even  in  the 
vicinity  of  Lyons.  Here  we  may  assume  that 
the  old  Draba  verna  has  produced  a  host  or  a 
swarm  of  new  types.  Thence  they  must  have 
spread  over  Europe,  but  whether  in  doing  so 
they  have  remained  constant,  or  whether  some 
or  many  of  them  have  repeatedly  undergone 
specific  mutations,  is  of  course  unknown. 

The  main  fact  is,  that  such  a  small  species  as 
Draba  verna  is  not  at  all  a  uniform  type,  but 
comprises  over  two  hundred  well  distinguished 
and  constant  forms. 

It  is  readily  granted  that  violets  and  whitlow- 
grasses  are  extreme  instances  of  systematic 
variability.  Such  great  numbers  of  elementary 
species  are  not  often  included  in  single  species 
of  the  system.  But  the  numbers  are  of  second- 
ary importance,  and  the  fact  that  systematic 
species  consist,  as  a  rule,  of  more  than  one  inde- 
pendent and  constant  subspecies,  retains  its  al- 
most universal  validity. 

In  some  cases  the  systematic  species  are  man- 
ifest groups,  sharply  differentiated  from  one 
another.  In  other  instances  the  groups  of  ele- 
mentary forms  as  they  are  shown  by  direct  ob- 
servation, have  been  adjudged  by  many  authors 


52  Elementary  Species 

to  be  too  large  to  constitute  species.  Hence  the 
poljTQorphous  genera,  concerning  the  syste- 
matic subdivisions  of  which  hardly  two  authors 
agree.  Brambles  and  roses  are  widely  known 
instances,  but  oaks,  elms,  apples,  and  pears, 
Mentha,  Prunus,  Vitis,  Lactuca,  Cucumis,  Cu- 
curhita  and  numerous  others  are  in  the  same 
condition. 

In  some  instances  the  existence  of  elementary 
species  is  so  obvious,  that  they  have  been  de- 
scribed by  taxonomists  as  systematic  varieties 
or  even  as  good  species.  The  primroses  afford 
a  widely  known  example.  Linnaeus  called  them 
Primula  veris,  and  recognized  three  types  as 
pertaining  to  this  species,  but  Jacquin  and 
others  have  elevated  these  subspecies  to  the  full 
rank  of  species.  They  now  bear  the  names  of 
Primula  elatior  with  larger,  P.  officinalis  with 
smaller  flowers,  and  P.  acaulis.  In  the  last 
named  the  common  flower-stalk  is  lacking  and 
the  flowers  of  the  umbel  seem  to  be  borne  in 
the  axils  of  the  basal  leaves. 

In  other  genera  such  nearly  allied  species  are 
more  or  less  universally  recognized.  Galium 
Mollugo  has  been  divided  into  G.  elatum  with  a 
long  and  weak  stem,  and  G.  erectum  with 
shorter  and  erect  stems ;  Cochlearia  danica,  an- 
glica  and  officinalis  are  so  nearly  allied  as  to  be 
hardly  distinguishable.    Sagina  apetala  and  pat- 


Elementary  Species  in  Nature  53 

ula,  Spergula  media  and  salina  and  many  other 
pairs  of  allied  species  have  differentiating  char- 
acters of  the  same  value  as  those  of  the  element- 
ary species  of  Drab  a  verna,  Filago,  Plant  ago, 
Carex,  Ficaria  and  a  long  series  of  other  genera 
afford  proofs  of  the  same  close  relation  be- 
tween smaller  and  larger  groups  of  species.  The 
European  frost-weeds  or  Helianthemum  in- 
clude a  group  of  species  which  are  so  closely  al- 
lied, that  ordinary  botanical  descriptions  are 
not  adequate  to  give  any  idea  of  their  differen- 
tiating features.  It  is  almost  impossible  to 
determine  them  by  means  of  the  common  ana- 
lytical keys.  They  have  to  be  gathered  from 
their  various  native  localities  and  cultivated 
side  by  side  in  the  garden  to  bring  out  their 
differences.  Among  the  species  of  France,  ac- 
cording to  Jordan,  Helianthemum  poUfoUum, 
H.  apennimim,  H.  pilosum  and  H.  pulverulen- 
tum  are  of  this  character. 

A  species  of  cinquefoil,  Potentilla  Tormen- 
tilla,  which  is  distinguished  by  its  quaternate 
flowers,  occurs  in  Holland  in  two  distinct  types, 
which  have  proved  constant  in  my  cultural  exper- 
iments. One  of  them  has  broad  petals,  meeting 
together  at  the  edges,  and  constituting  a  round- 
ed saucer  without  breaks.  The  other  has  nar- 
row petals,  which  are  strikingly  separated  from 
one  another  and  show  the  sepals  between  them. 


54  Elementary  Species 

In  the  same  manner  bluebells  vary  in  the  size 
and  shape  of  the  corolla,  which  may  be  wide  or 
narrow,  bell-shaped  or  conical,  with  the  tips 
turned  downwards,  sidewards  or  backwards. 

As  a  rule  all  of  the  more  striking  elementary 
types  have  been  described  by  local  botanists 
under  distinct  specific  names,  while  they  are 
thrown  together  into  the  larger  systematic  spe- 
cies by  other  authors,  who  study  the  distribu- 
tion of  plants  over  larger  portions  of  the 
world.  Everything  depends  on  the  point  of 
view  taken.  Large  floras  require  large  species. 
But  the  study  of  local  floras  yields  the  best  re- 
sults if  the  many  forms  of  the  region  are  distin- 
guished and  described  as  completely  as  possible, 
^nd  the  easiest  way  is  to  give  to  each  of  them  a 
specific  name.  If  two  or  more  elementary  spe- 
cies are  united  in  the  same  district,  they  are 
often  treated  in  this  way,  but  if  each  region  had 
its  own  type  of  some  given  species,  commonly 
the  part  is  taken  for  the  whole,  and  the  sundry 
forms  are  described  under  the  same  name,  with- 
out further  distinctions. 

Of  course  these  questions  are  all  of  a  practical 
and  conventional  nature,  but  involve  the  differ- 
ent methods  in  which  different  authors  deal 
with  the  same  general  fact.  The  fact  is  that 
systematic  species  are  compound  groups,  ex- 
actly like  the  genera  and  that  their  real  units 


Elementary  Species  in  Nature  55 

can  only  be  recognized  by  comparative  experi- 
mental studies. 

Though  the  evidence  already  given  might  be 
esteemed  to  be  sufficient  for  our  purpose,  I 
should  like  to  introduce  a  few  more  examples; 
two  of  them  pertain  to  American  plants. 

The  Ipecac  spurge  or  Euphorbia  Ipecacu- 
anha occurs  from  Connecticut  to  Florida, 
mainly  near  the  coast,  preferring  dry  and  sandy 
soil.  It  is  often  found  by  the  roadsides.  Ac- 
cording to  Britton  and  Brown's  "Illustrated 
Flora  "  it  is  glabrous  or  pubescent,  with  several 
or  many  stems,  ascending  or  nearly  erect ;  with 
green  or  red  leaves,  which  are  wonderfully 
variable  in  outline,  from  linear  to  orbicular, 
mostly  opposite,  the  upper  sometimes  whorled, 
the  lower  often  alternate.  The  glands  of  the 
involucres  are  elliptic  or  oblong,  and  even  the 
seeds  vary  in  shape. 

Such  a  wide  range  of  variability  evidently 
points  to  the  existence  of  some  minor  types. 
Dr.  John  Harshberger  has  made  a  study  of 
those  which  occur  in  the  vicinity  of  Whitings  in 
New  Jersey.  His  types  agree  with  the  descrip- 
tion given  above.  Others  were  gathered  by 
him  at  Brown's  Mills  in  the  pinelands.  New 
Jersey,  where  they  grew  in  almost  pure  sand  in 
the  bright  sunlight.  He  observed  still  other 
differentiating  characters.     The  amount  of  seed 


56  Elementary  Species 

produced  and  the  time  of  flowering  were  vari- 
able to  a  remarkable  degree. 

Dr.  Harshberger  had  the  kindness  to  send  me 
some  dried  specimens  of  the  most  interesting  of 
these  types.  They  show  that  the  peculiarities 
are  individual,  and  that  each  specimen  has  its 
own  characters.  It  is  very  probable  that  a 
comparative  experimental  study  will  prove  the 
existence  of  a  large  number  of  elementary  spe- 
cies, differing  in  many  points;  they  will  prob- 
ably also  show  differences  in  the  amount  of 
the  active  chemical  substances,  especially  of 
emetine,  which  is  usually  recorded  as  present  in 
about  V,  but  which  will  undoubtedly  be 
found  in  larger  quantities  in  some,  and  in 
smaller  quantities  in  other  elementary  species. 
In  this  way  the  close  and  careful  distinction  of 
the  really  existing  units  might  perhaps  prove 
of  practical  importance. 

Macfarlane  has  studied  the  beach-plum  or 
Pruniis  maritima,  which  is  abundant  along  the 
coast  regions  of  the  Eastern  States  from  Vir- 
ginia to  New  Brunswick.  It  often  covers  areas 
from  two  to  two  hundred  acres  in  extent,  some- 
times to  the  exclusion  of  other  plants.  It  is  most 
prolific  on  soft  drifting  sand  near  the  sea  or 
along  the  shore,  where  it  may  at  times  be  washed 
with  ocean-spray.  The  fruit  usually  become 
ripe  about  the  middle  of  August,  and  show  ex- 


Elementary  Species  in  Nature  57 

treme  variations  in  size,  shape,  color,  taste,  con- 
sistency and  maturation  period,  indicating  the 
existence  of  separate  races  or  elementary  spe- 
cies, with  widely  differing  qualities.  The  earlier 
varieties  begin  to  ripen  from  August  10  to  20, 
and  a  continuous  supply  can  be  had  till  Septem- 
ber 10,  while  a  few  good  varieties  continue  to 
ripen  till  September  20.  But  even  late  in  Octo- 
ber some  other  types  are  still  found  maturing 
their  fruits. 

Exact  studies  were  made  of  fruit  and  stone 
variations,  and  their  characteristics  as  to  color, 
weight,  size,  shape  and  consistency  were  fully 
described.  Similar  variations  have  been  ob- 
served, as  is  well  known,  in  the  cultivated 
plums.  Fine  blue-black  fruits  were  seen  on 
some  shrubs  and  purplish  or  yellow  fruits  on 
others.  Some  exhibit  a  firmer  texture  and 
others  a  more  watery  pulp.  Even  the  stones 
show  differences  which  are  suggestive  of  dis- 
tinct races. 

Kecently  Mr.  Luther  Burbank  of  Santa  Eosa, 
California,  has  made  use  of  the  beach-plum  to 
produce  useful  new  varieties.  He  observed 
that  it  is  a  very  hardy  species,  and  never  fails 
to  bear,  growing  under  the  most  trying  condi- 
tions of  dry  and  sandy,  or  of  rocky  and  even  of 
heavy  soil.  The  fruits  of  the  wild  shrubs  are 
utterly  worthless  for  anything  but  preserving. 


58  Elementary  Species 

But  by  means  of  crossing  with  other  species 
and  especially  with  the  Japanese  plums,  the 
hardy  qualities  of  the  beach-plum  have  been 
united  with  the  size,  flavor  and  other  valuable 
qualities  of  the  fruit,  and  a  group  of  new  plums 
have  been  produced  with  bright  colors,  ovoid  and 
globular  forms  which  are  never  flattened  and 
have  no  suture.  The  experiments  were  not  fin- 
ished, when  I  visited  Mr.  Burbank  in  July,  1904, 
and  still  more  startling  improvements  were  said 
to  have  been  secured. 

I  may  perhaps  be  allowed  to  avail  myself  of 
this  opportunity  to  point  out  a  practical  side  of 
the  study  of  elementary  species.  This  always 
appears  whenever  wild  plants  are  subjected  to 
cultivation,  either  in  order  to  reproduce  them  as 
pure  strains,  or  to  cross  them  with  other  al- 
ready cultivated  species.  The  latter  practice 
is  as  a  rule  made  use  of  whenever  a  wild  spe- 
cies is  found  to  be  in  possession  of  some  quality 
which  is  considered  as  desirable  for  the  culti- 
vated forms.  In  the  case  of  the  beach-plum 
it  is  the  hardiness  and  the  great  abundance  of 
fruits  of  the  wild  species  which  might  profit- 
ably be  combined  with  the  recognized  qualities 
of  the  ordinary  plums.  Now  it  is  manifest,  that 
in  order  to  make  crosses,  distinct  individual 
plants  are  to  be  chosen,  and  that  the  variability 
of  the  wild  species  may  be  of  very  great  im- 


Elementary  Species  in  Nature  59 

portance.  Among  the  range  of  elementary  spe- 
cies those  should  be  used  which  not  only  pos- 
sess the  desired  advantages  in  the  highest  de- 
gree, but  which  promise  the  best  results  in  other 
respects  or  their  earliest  attainment.  The 
fuller  our  knowledge  of  the  elementary  species 
constituting  the  systematic  groups,  the  easier 
and  the  more  reliable  will  be  the  choice  for  the 
breeder.  Many  Californian  wild  flowers  with 
bright  colors  seem  to  consist  of  large  numbers 
of  constant  elementary  forms,  as  for  instance, 
the  lilies,  godetias,  eschscholtias  and  others. 
They  have  been  brought  into  cultivation  many 
times,  but  the  minutest  distinction  of  their  ele- 
mentary forms  is  required  to  attain  the  highest 
success. 

In  concluding,  I  will  point  out  a  very  interest- 
ing difficulty,  which  in  some  cases  impedes  the 
clear  understanding  of  elementary  species.  It 
is  the  lack  of  self-fertilization.  It  occurs  in 
widely  distant  families,  but  has  a  special  inter- 
est for  us  in  two  genera,  which  are  generally 
known  as  very  polymorphous  groups. 

One  of  them  is  the  hawkweed  or  Hieracium, 
and  the  other  is  the  dandelion  or  Taraxacum 
officinale.  Hawkweeds  are  known  as  a  genus 
in  which  the  delimitation  of  the  species  is  al- 
most impossible.  Thousands  of  forms  may  be 
cultivated  side  by  side  in  botanical  gardens,  ex- 


60  Elementary  Species 

hibiting  slight  but  undoubted  differentiating 
features,  and  reproduce  themselves  truly  by 
seed.  Descriptions  were  formerly  difficult  and 
so  complicated  that  the  ablest  writers  on  this 
genus,  Fries  and  Xageli  are  said  not  to  have 
been  able  to  recognize  the  separate  species  by 
the  descriptions  given  by  each  other.  Are  these 
types  to  be  considered  as  elementary  species, 
or  only  as  individual  differences?  The  decis- 
ion of  course,  would  depend  upon  their  behav- 
ior in  cultures.  Such  tests  have  been  made  by 
various  experimenters.  In  the  dandelion  the 
bracts  of  the  involucre  give  the  best  characters. 
The  inner  ones  may  be  linear  or  linear-lance- 
olate, with  or  without  appendages  below  the  tip ; 
the  outer  ones  may  be  similar  and  only  shorter, 
or  noticeably  larger,  erect,  spreading  or  even 
reflexed,  and  the  color  of  the  involucre  may  be 
a  pure  green  or  glaucous;  the  leaves  may  be 
nearly  entire  or  pinnatifid,  or  sinuate-dentate, 
or  very  deeply  runcinate-pinnatifid,  or  even 
pinnately  divided,  the  whole  plant  being  more 
or  less  glabrous. 

Raunkiaer,  who  has  studied  experimentally  a 
dozen  types  from  Denmark,  found  them  con- 
stant, but  observed  that  some  of  them  have  no 
pollen  at  all,  while  in  others  the  pollen,  though 
present,  is  impotent.  It  does  not  germinate  on 
the  stigma,  cannot  produce  the  ordinary  tube, 


Elementary  Species  in  Nature  61 

and  hence  has  no  fertilizing  power.  But  the 
young  ovaries  do  not  need  such  fertilization. 
They  are  sufficient  unto  themselves.  One  may 
cut  off  all  the  flowers  of  a  head  before  the  open- 
ing of  the  anthers,  and  leave  the  ovaries 
untouched,  and  the  head  will  ripen  its  seeds 
quite  as  well.  The  same  thing  occurs  in  the 
hawkweeds.  Here,  therefore,  we  have  no  ferti- 
lization and  the  extensive  widening  of  the  varia- 
bility, which  generally  accompanies  this  pro- 
cess is,  of  course,  wanting.  Only  partial  or 
vegetative  variability  is  present.  Unfertilized 
eggs  when  developing  into  embryos  are  equiva- 
lent to  buds,  separated  from  the  parent-plant 
and  planted  for  themselves.  They  repeat  both 
the  specific  and  the  individual  characters  of 
the  parent.  In  the  case  of  the  hawkweed  and 
the  dandelion  there  is  at  present  no  means  of 
distinguishing  between  these  two  contrasting 
causes  of  variability.  But  like  the  garden- 
varieties  which  are  always  propagated  in  the 
vegetative  way,  their  constancy  and  uniformity 
are  only  apparent  and  afford  no  real  indication 
of  hereditary  qualities. 

In  addition  to  these  and  other  exceptional 
cases,  seed-cultures  are  henceforth  to  be  con- 
sidered as  the  sole  means  of  recognizing  the 
really  existing  systematic  units  of  nature.  All 
other  groups,  including  systematic  species  and 


62  Elementary  Species 

genera,  are  equallj^  artificial  or  conventional. 
In  other  words  we  may  state  ''  that  current 
misconceptions  as  to  the  extreme  range  of  fluc- 
tuating variability  of  many  native  species  have 
generally  arisen  from  a  failure  to  recognize  the 
composite  nature  of  the  forms  in  question,"  as 
has  been  demonstrated  by  MacDougal  in  the 
case  of  the  common  evening-primrose,  Oeno- 
thera hiennis.  *'  It  is  evident  that  to  study  the 
behavior  of  the  characters  of  plants  we  must 
have  them  in  their  simplest  combinations;  to 
investigate  the  origin  and  movements  of  species 
we  must  deal  with  them  singly  and  uncompli- 
cated. ' ' 


Lecture  III 

ELEMENTARY    SPECIES    OF    CULTIVATED    PLANTS 

Recalling  the  results  of  the  last  lecture,  we 
see  that  the  species  of  the  sj^stematists  are  not 
in  reality  units,  though  in  the  ordinary  course 
of  floristic  studies  they  may,  as  a  rule,  seem  to 
be  so.  In  some  cases  representatives  of  the 
same  species  from  different  countries  or  re- 
gions, when  compared  with  one  another  do  not 
exactly  agree.  Many  species  of  ferns  afford 
instances  of  this  rule,  and  Lindley  and  other 
great  systematists  have  frequently  been  puz- 
zled by  the  wide  range  of  differences  between 
the  individuals  of  a  single  species. 

In  other  cases  the  differing  forms  are  ob- 
served to  grow  near  each  other,  sometimes  in 
neighboring  provinces,  sometimes  in  the  same 
locality,  growing  and  flowering  in  mixtures  of 
two  or  three  or  even  more  elementary  types. 
The  violets  exhibit  widespread  ancient  types, 
from  which  the  local  species  may  be  taken  to 
have  arisen.  The  common  ancestors  of  the 
whitlow-grasses  are  probably  not  to  be  found 

63 


64  Elementary  Species 

among  existing  forms,  but  nmnerous  types  are 
crowded  together  in  the  southern  part  of  central 
Europe  and  more  thinly  scattered  elsewhere, 
even  as  far  as  western  Asia.  There  can  be  lit- 
tle doubt  that  their  common  origin  is  to  be 
sought  in  the  center  of  their  geographic  dis- 
tribution. 

Numerous  other  cases  exhibit  smaller  num- 
bers of  elementary  units  within  a  systematic 
species;  in  fact  purely  uniform  species  seem 
to  be  relatively  rare.  But  with  small  num- 
bers there  are  of  course  no  indications  to 
be  expected  concerning  their  common  origin  or 
the  starting  point  of  their  distribution. 

It  is  manifest  that  these  experiences  with  wild 
species  must  find  a  parallel  among  cultivated 
plants.  Of  course  cultivated  plants  were  origi- 
nally wild  and  must  have  come  under  the  gen- 
eral law.  Hence  we  may  conclude  that  when 
first  observed  and  taken  up  by  man,  they  must 
already  have  consisted  of  sundry  elementary 
subspecies.  And  we  may  confidently  assert 
that  some  must  have  been  rich  and  others  poor 
in  such  types. 

Granting  this  state  of  things  as  the  only  prob- 
able one,  we  can  easily  imagine  what  must  have 
been  the  consequences.  If  a  wild  species  had 
been  taken  into  cultivation  only  once,  the  culti- 
vated form  would  have  been  a  single  element- 


Cultivated  Elementary  Species  65 

ary  type.  But  it  is  not  very  likely  that  such 
partiality  would  occur  often.  The  conception 
that  different  tribes  at  different  times  and  in 
distant  countries  would  have  used  the  wild 
plants  of  their  native  regions  seems  far  more 
natural  than  that  all  should  have  obtained 
plants  for  cultivation  from  the  same  source  or 
locality.  If  this  theory  may  be  relied  upon, 
the  origin  of  many  of  the  more  widely  cultivated 
agricultural  plants  must  have  been  multiple, 
and  the  number  of  the  original  elementary  spe- 
cies of  the  cultivated  types  must  have  been  so 
much  the  larger,  the  more  widely  distributed 
and  variable  the  plants  under  consideration 
were  before  the  first  period  of  cultivation. 

Further  it  would  seem  only  natural  to  explain 
the  wide  variability  of  many  of  our  larger  agri- 
cultural and  horticultural  stocks  by  such  an  in- 
cipient multiformity  of  the  species  themselves. 
Through  commercial  intercourse  the  various 
types  might  have  become  mixed  so  as  to  make  it 
quite  impossible  to  point  out  the  native  locali- 
ties for  each  of  them. 

Unfortunately  historical  evidence  on  this 
point  is  almost  wholly  lacking.  The  differences 
in  question  could  not  have  been  appreciated  at 
that  remote  period,  and  interest  the  common  ob- 
server but  little  even  today.  The  history  of 
most  of  the  cultivated  plants  is  very  obscure. 


66  Elementary  Species 

and  even  the  most  skillful  historians,  by  sifting 
the  evidence  afforded  by  the  older  writers,  and 
that  obtained  by  comparative  linguistic  investi- 
gations have  been  able  to  do  little  more  than 
frame  the  most  general  outline  of  the  cultural 
history  of  the  most  common  and  most  widely 
used  plants. 

Some  authors  assume  that  cultivation  itself 
might  have  been  the  principal  cause  of  variabil- 
ity, but  it  is  not  proved,  nor  even  ]3robable,  that 
cultivated  plants  are  intrinsically  more  variable 
than  their  wild  prototypes.  Appearances  in 
this  case  are  very  deceptive.  Of  course  widely 
distributed  plants  are  as  a  rule  richer  in  subspe- 
cies than  forms  with  limited  distribution,  and 
the  former  must  have  had  a  better  chance  to  be 
taken  into  cultivation  than  the  latter.  In  many 
cases,  especially  with  the  more  recent  cultivated 
species,  man  has  deliberately  chosen  variable 
forms,  because  of  their  greater  promise. 
Thirdly,  wide  variability  is  the  most  efficient 
means  of  acclimatization,  and  only  species  with 
many  elementary  units  would  have  offered 
the  adequate  material  for  introduction  into  new 
countries. 

From  this  discussion  it  would  seem  that  it  is 
more  reasonable  to  assert  that  variability  is  one 
of  the  causes  of  the  success  of  cultivation,  than 
to  assume  that  cultivation  is  a  cause  of  variabil- 


Cultivated  Elementary  Species  67 

ity  at  large.  And  this  assumption  would  be 
equally  sufficient  to  explain  the  existing  condi- 
tions among  cultivated  plants. 

Of  course  I  do  not  pretend  to  say  that  culti- 
vated plants  should  be  expected  to  be  less  vari- 
able than  in  the  wild  state,  or  that  swarms  of 
elementary  species  might  not  be  produced  dur- 
ing cultivation  quite  as  well  as  before.  How- 
ever the  chance  of  such  an  event,  as  is  easily 
seen,  cannot  be  very  great,  and  we  shall  have  to 
be  content  with  a  few  examples  of  which  the 
coconut  is  a  notable  one. 

Leaving  this  general  discussion  of  the  sub- 
ject, we  may  take  up  the  example  of  the  beets. 
The  sugar-beet  is  only  one  type  from  among  a 
horde  of  others,  and  though  the  origin  of  all  the 
single  types  is  not  historically  known,  the  plant 
is  frequently  found  in  the  wild  state  even  at  the 
present  time,  and  the  native  types  may  be  com- 
pared with  the  corresponding  cultivated  varie- 
ties. 

The  cultivation  of  beets  for  sugar  is  not  of 
very  ancient  date.  The  Romans  knew  the  beets 
and  used  them  as  vegetables,  both  the  roots  and 
the  leaves.  They  distinguished  a  variety  with 
white  and  one  with  red  flesh,  but  whether  they 
cultivated  them,  or  only  collected  them  from 
where  they  grew  spontaneously,  appears  to  be 
unknown. 


68  Elementary  Species 

Beets  are  even  now  found  in  large  quantities 
along  the  shores  of  Italy.  They  prefer  the 
vicinity  of  the  sea,  as  do  so  many  other  mem- 
bers of  the  beet-family,  and  are  not  limited  to 
Italy,  but  are  found  growing  elsewhere  on  the 
littoral  of  the  Mediterranean,  in  the  Canary 
Islands  and  through  Persia  and  Babylonia  to 
India.  In  most  of  their  native  localities  they 
occur  in  great  abundance. 

The  color  of  the  foliage  and  the  size  of  the 
roots  are  extremely  variable.  Some  have  red 
leafstalks  and  veins,  others  a  uniform  red  or 
green  foliage,  some  have  red  or  white  or  yellow 
roots,  or  exhibit  alternating  rings  of  a  red  and 
of  a  white  tinge  on  cut  surfaces.  It  seems  only 
natural  to  consider  the  white  and  the  red,  and 
even  the  variegated  types  as  distinct  varieties, 
which  in  nature  do  not  transgress  their  limits 
nor  change  into  one  another.  In  a  subsequent 
lecture  I  will  show  that  this  at  least  is  the  rule 
with  the  corresponding  color-varieties  in  other 
genera. 

The  fleshiness  or  pulpiness  of  the  roots  is  still 
more  variable.  Some  are  as  thick  as  the  arm 
and  edible,  others  are  not  thicker  than  a  finger 
and  of  a  woody  composition,  and  the  structure 
of  this  woody  variety  is  very  interesting.  The 
sugar-beet  consists,  as  is  generally  known,  of 
concentric  layers  of  sugar-tissue  and  of  vascu- 


Cultivated  Elementary  Species  69 

lar  strands;  the  larger  the  first  and  the 
smaller  the  latter,  the  greater  is,  as  a  rule,  the 
average  amount  of  sugar  of  the  race.  Through 
the  kindness  of  the  late  Mr.  Rimpau,  a  well- 
known  German  breeder  of  sugar-beet  varieties, 
I  obtained  specimens  from  seed  of  a  native  wild 
locality  near  Bukharest.  The  plants  produced 
quite  woody  roots,  showing  almost  no  sugar- 
tissue  at  all.  Woody  layers  of  strongly  de- 
veloped fibrovascular  strands  were  seen  to  be 
separated  one  from  another  only  by  very  thin 
layers  of  parenchymatous  cells.  Even  the 
number  of  layers  is  variable ;  it  was  observed  to 
be  five  in  my  plants ;  but  in  larger  roots  double 
this  number  and  even  more  may  easily  be  met 
with. 

Some  authors  have  distinguished  specific 
types  among  these  wild  forms.  While  the 
cultivated  beets  are  collected  under  the  head  of 
Beta  vulgaris,  separate  types  with  more  or  less 
woody  roots  have  been  described  as  Beta  mari- 
tima  and  Beta  patula.  These  show  differences 
in  the  habit  of  the  stems  and  the  foliage.  Some 
have  a  strong  tendency  to  become  annual, 
others  to  become  biennial.  The  first  of  course 
do  not  store  a  large  quantity  of  food  in  their 
roots,  and  remain  thin,  even  at  the  time  of  flow- 
ering. The  biennial  types  occur  in  all  sizes  of 
roots.     In  the  annuals  the  stems  may  vary  from 


70  Elementary  Species 

erect  to  ascending,  and  the  name  patula  indi- 
cates stems  which  are  densely  branching  from 
the  base  with  widely  spreading  branches 
throughout.  Mr.  Em.  von  Proskowetz  of  Kwas- 
sitz,  Austria,  kindly  sent  me  seeds  of  this  Beta 
patula,  the  variability  of  which  was  so  great  in 
my  cultures  as  to  range  from  nearly  typical 
sugar-beets  to  the  thin  woody  type  of  Buk- 
harest. 

Broad  and  narrow  leaves  are  considered  to  be 
differentiating  marks  between  Beta  vulgaris 
and  Beta  patula,  but  even  here  a  wide  range  of 
forms  seem  to  occur. 

Rimpau,  Proskowetz,  Schindler  and  others 
have  made  cultures  of  beets  from  wild  localities 
in  order  to  discover  a  hypothetical  common  an- 
cestor of  all  the  present  cultivated  types. 
These  researches  point  to  the  B.  patula  as  the 
probable  ancestor,  but  of  course  they  were  not 
made  to  decide  the  question  as  to  whether  the 
origination  of  the  several  now  existing  types 
had  taken  place  before  or  during  culture. 
From  a  general  point  of  view  the  variability  of 
the  wild  species  is  parallel  to  that  of  the 
cultivated  forms  to  such  a  degree  as  to  suggest 
the  multiple  origin  of  the  former.  But  a  close 
investigation  of  this  highly  important  prob- 
lem has  still  to  be  made. 

The  varieties  of  the  cultivated  beets  are  com- 


Cultivated  Elementary  Species  71 

monly  included  in  four  subspecies.  The  two 
smallest  are  the  salad-beets  and  the  ornamental 
forms,  the  first  being  used  as  food,  and  ordinar- 
ily cultivated  in  red  varieties,  the  second  be- 
ing used  as  ornamental  plants  during  the  fall, 
when  they  fill  the  beds  left  empty  by  summer 
flowers,  with  a  bright  foliage  that  is  exceedingly 
rich  in  form  and  color.  Of  the  remaining  sub- 
species, one  comprises  the  numerous  sorts  culti- 
vated as  forage-crops  and  the  other  the  true 
sugar-beets.  Both  of  them  vary  widely  as  to 
the  shape  and  the  size  of  the  roots,  the  quality 
of  the  tissue,  the  foliage  and  other  characteris- 
tics. 

Some  of  these  forms,  no  doubt,  have  origi- 
nated during  culture.  Most  of  them  have  been 
improved  by  selection,  and  no  beet  found  in  the 
wild  state  ever  rivals  any  cultivated  variety. 
But  the  improvement  chiefly  atf ects  the  size,  the 
amount  of  sugar  and  nutrient  substances  and 
some  other  qualities  which  recur  in  most  of  the 
varieties.  The  varietal  attributes  themselves 
however,  are  more  or  less  of  a  specific  nature, 
and  have  no  relation  to  the  real  industrial 
value  of  the  race.  The  short-rooted  and  the 
horn-shaped  varieties  might  best  be  cited  as 
examples. 

The  assertion  that  the  sundry  varieties  of 
forage-beets  are  not  the  result  of  artificial  selec- 


72  Elementary  Species 

tion,  is  supported  in  a  large  measure  by  the  his- 
toric fact  that  the  most  of  them  are  far  older 
than  the  method  of  conscious  selection  of  plants 
itself.  This  method  is  due  to  Louis  Vilmorin 
and  dates  from  the  middle  of  the  last  century. 
But  in  the  sixteenth  century  most  of  our  present 
varieties  of  beets  were  already  in  cultivation. 
Caspar  Bauhin  gives  a  list  of  the  beets  of  his 
time  and  it  is  not  difficult  to  recognize  in  it  a 
large  series  of  subspecies  and  varieties  and 
even  of  special  forms,  which  are  still  cul- 
tivated. A  more  complete  list  was  published 
towards  the  close  of  the  same  century  by  Olivier 
de  Serres  in  his  world-renowned  ^'  Theatre 
d 'Agriculture  "  (Paris,  1600). 

The  red  forage-beets  which  are  now  cultivated 
on  so  large  a  scale,  had  been  introduced  from 
Italy  into  France  only  a  short  time  before. 

From  this  historic  evidence,  the  period  during 
which  the  beets  were  cultivated  from  the  time 
of  the  Eomans  or  perhaps  much  later,  up  to  the 
time  of  Bauhin  and  De  Serres,  would  seem  far 
too  short  for  the  production  by  the  unguided  se- 
lection of  man  of  all  the  now  existing  types.  On 
the  other  hand,  the  parallelism  between  the 
characters  of  some  wild  and  some  cultivated 
varieties  goes  to  make  it  very  probable  that 
other  varieties  have  been  found  in  the  same 
way,  some  in  this  country  and  others  in  that, 


Cultivated  Elementary  Species  73 

and  have  been  taken  into  cultivation  separately. 
Afterwards  of  course  all  must  have  been  im- 
proved in  the  direction  required  by  the  needs 
of  man. 

Quite  the  same  conclusion  is  aiforded  by  ap- 
ples. The  facts  are  to  some  extent  of  another 
character,  and  the  rule  of  the  derivation  of  the 
present  cultivated  varieties  from  original 
wild  forms  can  be  illustrated  in  this  case  in  a 
more  direct  way.  Of  course  we  must  limit  our- 
selves to  the  varieties  of  pure  ancestry  and 
leave  aside  all  those  which  are  of  hybrid  or  pre- 
sumably^ hybrid  origin. 

Before  considering  their  present  state  of  cul- 
ture, something  must  be  said  about  the  earlier 
history  and  the  wild  state  of  the  apples. 

The  apple-tree  is  a  common  shrub  in  woods 
throughout  all  parts  of  Europe,  with  the  only 
exception  of  the  extreme  north.  Its  distribu- 
tion extends  to  Anatolia,  the  Caucasus  and 
Ghilan  in  Persia.  It  is  found  in  nearly  all 
forests  of  any  extent  and  often  in  relatively 
large  numbers  of  individuals.  It  exhibits  vari- 
etal characters,  which  have  led  to  the  recog- 
nition of  several  spontaneous  forms,  especially 
in  France  and  in  Germany. 

The  differentiating  qualities  relate  to  the 
shape  and  indumentum  of  the  leaves.  Nothing 
is  known  botanically  as  to  differences  between 


74  Elementary  Species 

the  fruits  of  these  varieties,  but  as  a  matter  of 
fact  the  wild  apples  of  different  countries  are 
not  at  all  the  same. 

Alphonse  De  Candolle,  who  made  a  profound 
study  of  the  probable  origin  of  most  of  our  cul- 
tivated plants,  comes  to  the  conclusion  that  the 
apple-tree  must  have  had  this  wide  distribution 
in  ^prehistoric  times,  and  that  its  cultivation  be- 
gan in  ancient  times  everywhere. 

This  very  important  conclusion  by  so  high  an 
authority  throws  considerable  light  on  the  rela- 
tion between  cultivated  and  wild  varieties  at 
large.  If  the  historic  facts  go  to  prove  a  mul- 
tiple origin  for  the  cultivation  of  some  of  the 
more  important  useful  plants,  the  probability 
that  different  varieties  or  elementary  species 
have  been  the  starting  points  for  different  lines 
of  culture,  evidently  becomes  stronger. 

Unfortunatelv,  this  historic  evidence  is 
scanty.  The  most  interesting  facts  are  those 
concerning  the  use  of  apples  by  the  Romans 
and  by  their  contemporaries  of  the  Swiss  and 
middle  European  lake-dwellings.  Oswald  Heer 
has  collected  large  numbers  of  the  relics  of  this 
prehistoric  period.  Apples  were  found  in 
large  quantities,  ordinarily  cut  into  halves  and 
with  the  signs  of  having  been  dried.  Heer  dis- 
tinguished two  varieties,  one  with  large  and 
one  with  small  fruits.     The  first  about  3  and 


Cultivated  Elementary  Species  75 

the  other  about  1.5-2  cm.  in  diameter.  Both  are 
therefore  very  small  compared  with  our  present 
ordinary  varieties,  but  of  the  same  general  size 
as  the  wild  forms  of  the  present  day.  Like  these, 
they  must  have  been  of  a  more  woody  and  less 
fleshy  tissue.  They  would  scarcely  have  been 
tasteful  to  us,  but  in  ancient  times  no  better 
varieties  were  known  and  therefore  no  compari- 
son was  possible. 

There  is  no  evidence  concerning  the  question, 
as  to  whether  during  the  periods  mentioned  ap- 
ples were  cultivated  or  only  collected  in  the  wild 
state.  The  very  large  numbers  which  are 
found,  have  induced  some  writers  to  believe  in 
their  culture,  but  then  there  is  no  reason  why 
they  should  not  have  been  collected  in  quantity 
from  wild  shrubs.  The  main  fact  is  that  the 
apple  was  not  a  uniform  species  in  prehistoric 
times  but  showed  even  then  at  least  some 
amount  of  variability. 

At  the  present  day  the  wild  apples  are  very 
rich  in  elementary  species.  Those  of  Ver- 
sailles are  not  the  same  as  those  of  Belgium, 
and  still  others  are  growing  in  England  and  in 
Germany.  The  botanical  differences  derived 
from  the  blossoms  and  the  leaves  are  slight,  but 
the  flavor,  size  and  shape  of  the  fruits  diverge 
widely.  Two  opinions  have  been  advanced  to 
explain   this   high   degree    of  variability,   but 


76  Elementary  Species 

neither  of  tliem  conveys  a  real  explanation; 
their  aim  is  chiefly  to  support  different  views  as 
to  the  causes  of  variability,  and  the  origin  of 
elementary  species  at  large. 

One  opinion,  advocated  by  De  Candolle,  Dar- 
win and  others,  claims  that  the  varieties  owe 
their  origin  to  the  direct  influence  of  cultiva- 
tion, and  that  the  corresponding  forms  found 
in  the  wild  state,  are  not  at  all  original,  but  have 
escaped  from  cultivation  and  apparently  be- 
come wild.  Of  course  this  possibility  cannot 
be  denied,  at  least  in  any  single  instance,  but  it 
seems  too  sweeping  an  assertion  to  make  for 
the  whole  range  of  observed  forms. 

The  alternative  theory  is  that  of  van  Mons, 
the  Belgian  originator  of  commercial  varieties 
of  apples,  who  has  published  his  experiments  in 
a  large  work  called  '  ^  Arbres  f ruitiers  ou  Pomo- 
nomie  beige. ' '  Most  of  the  more  remarkable  ap- 
ples of  the  first  half  of  the  last  century  were  pro- 
duced by  van  Mons,  but  his  greatest  merit  is 
not  the  direct  production  of  a  number  of  good 
varieties,  but  the  foundation  of  the  method,  by 
which  new  varieties  may  be  obtained  and  im- 
proved. 

According  to  van  Mons,  the  production  of  a 
new  variety  consists  chiefly  of  two  parts.  The 
first  is  the  discovery  of  a  subspecies  with  new 
desirable  qualities.     The  second  is  the  trans- 


Cultivated  Elementary  Species  77 

formation  of  the  original  small  and  woody  ap- 
ple into  a  large,  fleshy  and  palatable  variety. 
Subspecies,  or  what  we  now  call  elementary 
species  were  not  produced  by  man ;  nature  alone 
creates  new  forms,  as  van  Mons  has  it.    He  ex- 
amined with  great  care  the  wild  apples  of  his 
country,  and  especially  those  of  the  Ardennes, 
and  found  among  them  a  number  of  species 
with  different  flavors.     For  the  flavor  is  the 
one  great  point,  which  must  be  found  ready  in 
nature    and  which  may  be  improved,  but  can 
never  be  created  by  artificial  selection.     The 
numerous  differences  in  flavor  are  quite  orig- 
inal; all  of  them  may  be  found  in  the  wild 
state    and  most  of  them  even  in  so  limited  a 
region  as  the  Ardennes  Mountains.    Of  course 
van   Mons    preferred   not   to    start   from   the 
wild  types  themselves,  when  the  same  flavor 
could  be  met  with  in  some  cultivated  variety. 
His  general  method  was,  to  search  for  a  new 
flavor   and  to  try  to  bring  the  bearer  of  it  up 
to  the  desired  standard  of  size  and  edibility. 

The  latter  improvement,  though  it  always 
makes  the  impression  of  an  achievement,  is  only 
the  last  stone  to  be  added  to  the  building  up  of 
the  commercial  value  of  the  variety.  Without 
it,  the  best  flavored  apple  remains  a  crab ;  with 
it,  it  becomes  a  conquest.  According  to  the 
method  of  van  Mons  it  mav  be  reached  within 


78  Elementary  Species 

two  or  three  generations,  and  a  man's  life  is 
wholly  sufficient  to  produce  in  this  way  many 
new  types  of  the  very  best  sorts,  as  van  Mons 
himself  has  done.  It  is  done  in  the  usual  way, 
sowing  on  a  large  scale  and  selecting  the  best, 
which  are  in  their  turn  brought  to  an  early 
maturation  of  their  fruit  by  grafting,  because 
thereby  the  life  from  seed  to  seed  may  be  re- 
duced to  a  few  years. 

Form,  taste,  color,  flavor  and  other  valuable 
marks  of  new  varieties  are  the  products  of 
nature,  says  van  Mons,  only  texture,  fleshiness 
and  size  are  added  by  man.  And  this  is  done  in 
each  new  variety  by  the  same  method  and  ac- 
cording to  the  same  laws.  The  richness  of  the 
cultivated  apples  of  the  present  day  was  al- 
ready present  in  the  large  range  of  original 
wild  elementary  species,  though  unobserved 
and  requiring  improvement. 

An  interesting  proof  of  this  principle  is  af- 
forded by  the  experience  of  Mr.  Peter  M. 
Gideon,  as  related  by  Bailey.  Gideon  sowed 
large  quantities  of  apple-seeds,  and  one  seed 
produced  a  new  and  valuable  variety  called  by 
him  the  ' '  Wealthy  ' '  apple.  He  first  planted  a 
bushel  of  apple-seeds,  and  then  every  year,  for 
nine  years,  planted  enough  seeds  to  produce 
a  thousand  trees.  At  the  end  of  ten  years  all 
seedlings  had  perished  except  one  hardy  seed- 


Cultivated  Elementary  Species  79 

ling  crab.  This  experiment  was  made  in  Min- 
nesota, and  failed  wholly.  Then  he  bought  a 
small  lot  of  seeds  of  apples  and  crab-apples  in 
Maine  and  from  these  the  ''  Wealthy  ''  came. 
There  were  only  about  fifty  seeds  in  the  lot  of 
crab-apple  seed  which  produced  the  ' '  Wealthy, ' ' 
but  before  this  variety  was  obtained,  more  than 
a  bushel  of  seed  had  been  sown.  Chance  af- 
forded a  species  with  an  unknown  taste ;  but  the 
growing  of  many  thousands  of  seedlings  of 
known  varieties  was  not  the  best  means  to  get 
something  really  new. 

Pears  are  more  difficult  to  improve  than  ap- 
ples. They  often  require  six  or  more  genera- 
tions to  be  brought  from  the  wild  woody  state 
to  the  ordinary  edible  condition.  But  the  va- 
rieties each  seem  to  have  a  separate  origin,  as 
with  apples,  and  the  wide  range  of  form  and  of 
taste  must  have  been  present  in  the  wild  state, 
long  before  cultivation.  Only  recently  has  the 
improvement  of  cherries,  plums,  currants  and 
gooseberries  been  undertaken  with  success  by 
Mr.  Burbank,  and  the  difference  between  the 
wild  and  cultivated  forms  has  hitherto  been 
very  small.  All  indications  point  to  the  exist- 
ence, before  the  era  of  cultivation,  of  larger  or 
smaller  numbers  of  elementary  species. 

The  same  holds  good  with  many  of  the  larger 
forage  crops  and  other  plants  of  great  indus- 


80  Elementary  Species 

trial  value.  Clover  exhibits  many  varieties, 
which  have  been  cultivated  indiscriminately, 
and  often  in  motley  mixtures.  The  flower- 
heads  may  be  red  or  white,  large  or  small,  cylin- 
drie  or  rounded,  the  leaves  are  broader  or  nar- 
rower, with  or  without  white  spots  of  a  curious 
pattern.  They  may  be  more  or  less  hairy  and 
so  forth.  Even  the  seeds  exhibit  differences  in 
size,  shape  or  color,  and  of  late  Martinet  has 
shown,  that  by  the  simple  means  of  picking  out 
seeds  of  the  same  pattern,  pure  strains  of  clover 
may  be  obtained,  which  are  of  varying  cultural 
value.  In  this  way  the  best  subspecies  or  va- 
rieties may  be  sought  out  for  separate  cultiva- 
tion. Even  the  white  spots  on  the  leaflets  have 
proved  to  be  constant  characters  corresponding 
with  noticeable  differences  in  yield. 

Flax  is  another  instance.  It  was  already  cul- 
tivated, or  at  least  made  use  of  during  the 
period  of  the  lake-dwellers,  but  at  that  time  it 
was  a  species  referred  to  as  Linum  angusti- 
folium,  and  not  the  Linum  usitatissimiim,  which 
is  our  present  day  flax.  There  are  now  many 
subspecies,  elementary  species,  and  varieties 
under  cultivation.  The  oldest  of  them  is  known 
as  the  ^*  springing  flax,"  in  opposition  to  the 
ordinary  ''  threshing  flax."  It  has  capsules 
which  open  of  themselves,  in  order  to  dissemin- 
ate the  seeds,  while  the  ordinary  heads  of  the 


Cultivated  Elementary  Species  81 

flax  remain  closed  until  the  seeds  are  liberated 
by  threshing.  It  seems  probable  that  the  first 
form  or  Linum  crepitans  might  thrive  in  the 
wild  state  as  well  as  any  other  plant,  while  in 
the  common  species  those  qualities  are  lacking 
which  are  required  for  a  normal  dissemination 
of  the  seeds.  White  or  blue  flowers,  high  or 
dwarf  stems,  more  or  less  branching  at  the  base 
and  sundry  other  qualities  distinguish  the  va- 
rieties, aside  from  the  special  industrial  differ- 
ence of  the  fibres.  Even  the  life-history  varies 
from  annual  and  biennial,  to  perennial. 

It  would  take  us  too  long  to  consider  other  in- 
stances. It  is  well  known  that  corn,  though 
considered  as  a  single  botanical  species,  is  rep- 
resented by  different  subspecies  and  varieties 
in  nearly  every  region  in  which  it  is  grown.  Of 
course  its  history  is  unknown  and  it  is  impossi- 
ble to  decide  whether  all  the  tall  and  dwarf 
forms,  or  starchy  and  sweet  varieties,  dented 
or  rounded  kernels,  and  hundreds  of  others  are 
older  than  culture  or  have  come  into  existence 
during  historic  times,  or  as  some  assume, 
through  the  agency  of  man.  But  our  main 
point  now  is  not  the  origin,  but  only  the 
existence  of  constant  and  sharply  differentiated 
forms  within  botanical  species.  Nearly  every 
cultivated  plant  affords  instances  of  such  di- 
versity.    Some  include  a  few  types  only,  while 


82  Elementary  Species 

others  show  a  large  number  of  forms  clearly 
separated  to  a  greater  or  lesser  degree. 

In  some  few  instances  it  is  obvious  that  this 
variability  is  of  later  date  than  culture.  The 
most  conspicuous  case  is  that  of  the  coconut. 
This  valuable  palm  is  found  on  nearly  all  tropi- 
cal coasts,  in  America,  as  well  as  in  Asia,  but  in 
Africa  and  Australia  there  are  many  hun- 
dreds of  miles  of  shore  line,  where  it  is  not 
found.  Its  importance  is  not  at  all  the  same 
everywhere.  On  the  shores  and  islands  of  the 
Indian  Ocean  and  the  Malay  Archipelago,  man 
is  chiefly  dependent  upon  it,  but  in  America  it  is 
only  of  subordinate  usefulness. 

In  connection  with  these  facts,  it  abounds  in 
subspecies  and  varieties  in  the  East  Indian  re- 
gions, but  on  the  continent  of  America  little  at- 
tention has  as  yet  been  given  to  its  diverging 
qualities.  In  the  Malayan  region  it  affords  near- 
ly all  that  is  required  by  the  inhabitants.  The 
value  of  its  fruit  as  food,  and  the  delicious 
beverage  which  it  yields,  are  well  known. 
The  fibrous  rind  is  not  less  useful;  it  is 
manufactured  into  a  kind  of  cordage,  mats 
and  floor-cloths.  An  excellent  oil  is  obtained 
from  the  kernel  by  compression.  The  hard 
covering  of  the  stem  is  converted  into  drums 
and  used  in  the  construction  of  huts ;  the  lower 
part  is  so  hard  as  to  take  on  a  beautiful  polish 


Cultivated  Elementary  Species  83 

when  it  resembles  agate.  Finally  the  un- 
expanded  terminal  bud  is  a  delicate  article  of 
food.  Many  other  uses  could  be  mentioned,  but 
these  may  suffice  to  indicate  how  closely  the  life 
of  the  inhabitants  is  bound  up  with  the  culture 
of  this  palm,  and  how  sharply,  in  consequence, 
its  qualities  must  have  been  watched  by  early 
man.  Any  divergence  from  the  ordinary  type 
must  have  been  noted;  those  which  were  in- 
jurious must  have  been  rejected,  but  the  useful 
ones  must  have  been  appreciated  and  propa- 
gated. In  a  word  any  degree  of  variability 
afforded  by  nature  must  have  been  noticed  and 
cultivated. 

More  than  fifty  different  sorts  of  the  coco- 
nut are  described  from  the  Indian  shores  and 
islands,  with  distinct  local  and  botanical  names. 
Miquel,  who  was  one  of  the  best  systematists  of 
tropical  plants,  of  the  last  century,  described  a 
large  number  of  them,  and  since,  more  have 
been  added.  Nearly  all  useful  qualities  vary  in 
a  higher  or  lesser  degree  in  the  different  varie- 
ties. The  fibrous  strands  of  the  rind  of  the 
nut  are  developed  in  some  forms  to  such  a 
length  and  strength  as  to  yield  the  industrial 
product  known  as  the  coir-fibre.  Only  three  of 
them  are  mentioned  by  Miquel  that  have 
this  quality,  the  Cocos  nucifera  rutila,  cupnli- 
formis  and  stupposa.    Among  them  the  rutila 


84  Elementary  Species 

yields  the  best  and  most  supple  fibres,  while 
those  of  the  stupposa  are  stiif  and  almost  un- 
bending. 

The  varieties  also  differ  greatly  in  size,  color, 
shape  and  quality,  and  the  trees  have  also  pe- 
culiar characteristics.  One  variety  exhibits 
leaves  which  are  nearly  entire,  the  divisions  be- 
ing only  imperfectly  separated,  as  often  occurs 
m  the  very  first  leaves  of  the  seedlings  of  other 
varieties.  The  flavor  of  the  flesh,  oil  and  milk 
likewise  yield  many  good  varietal  marks. 

In  short,  the  coconut-palm  comes  under  the 
general  rule,  that  botanical  species  are  built  up 
of  a  number  of  sharply  distinguishable  types, 
which  prove  their  constancy  and  relative  inde- 
pendence by  their  wide  distribution  in  culture. 
In  systematic  works  all  these  forms  are  called 
varieties,  and  a  closer  investigation  of  their 
real  systematic  value  has  not  yet  been  made. 
But  the  question  as  to  the  origin  of  the  varieties 
and  of  the  coconut  itself  has  engrossed  the  at- 
tention of  many  botanists,  among  whom  are  De 
Candolle  in  the  middle  of  the  last  century,  and 
Cook  at  its  close. 

Both  questions  are  closely  connected.  De 
Candolle  claimed  an  Asiatic  origin  for  the  whole 
species,  while  Cook's  studies  go  to  prove  that 
its  original  habitat  is  to  be  sought  in  the  north- 
ern countries   of   South   America.    Numerous 


Cultivated  Elementarti  Species  85 

varieties  are  growing  in  Asia  and  have  as  yet 
not  been  observed  to  occur  in  America,  where 
the  coconut  is  only  of  subordinate  importance, 
being  one  of  many  useful  plants,  and  not  the 
only  one  relied  upon  by  the  natives  for  their  sub- 
sistence. If  therefore,  De  Candolle's  opinion 
is  the  right  one,  the  question  as  to  whether  the 
varieties  are  older  or  younger  than  the  culti- 
vated forms  of  the  species,  must  always  remain 
obscure.  But  if  the  proofs  of  an  American 
origin  should  be  forthcoming,  the  possibility, 
and  even  the  probability  that  the  varieties  are 
of  later  date  than  the  begining  of  their  culture, 
and  have  originated  while  in  this  condition  must 
at  once  be  granted.  An  important  point  in  the 
controversy  is  the  manner  in  which  the  coco- 
nuts were  disseminated  from  shore  to  shore, 
from  island  to  island.  De  Candolle,  Darwin 
and  most  of  the  European  writers  claim  that  the 
dispersal  was  by  natural  agencies,  such  as 
ocean-currents.  They  point  out  that  the  fibrous 
rind  or  husk  would  keep  the  fruits  afloat,  and 
uninjured,  for  many  days  or  even  many  weeks, 
while  being  carried  from  one  country  to  another 
in  a  manner  that  would  explain  their  geographic 
distribution.  But  the  probability  of  the  nuts  be- 
ing thrown  upon  the  strand,  and  far  enough 
from  the  shore  to  find  suitable  conditions  for 
their  germination,  is  a  very  small  one.     To  in- 


86  Elementary  Species 

sure  healthy  aud  vigorous  seedlings  the  nuts 
must  be  fully  ripe,  after  which  planting  cannot 
be  safely  delayed  for  more  than  a  few  weeks.  If 
kept  too  moist  the  nuts  rot.  If  once  on  the 
shore,  and  allowed  to  lie  in  the  sun,  they  become 
overheated  and  are  thereby  destroyed;  if 
thrown  in  the  shade  of  other  shrubs  and  trees, 
the  seedlings  do  not  find  the  required  conditions 
for  a  vigorous  growth. 

Some  authors  have  taken  the  fibrous  rind  to 
be  especially  adapted  to  transport  by  sea,  but  if 
this  were  so,  this  would  argue  that  water  is 
the  normal  or  at  least  the  very  frequent  medium 
of  dissemination,  which  of  course  it  is  not.  "We 
may  claim  with  quite  as  much  right  that  the 
thick  husk  is  necessary  to  enable  the  heavy 
fruit  to  drop  from  tall  trees  with  safety.  But 
even  for  this  purpose  the  protection  is  not  suffi- 
cient, as  the  nuts  often  suffer  from  falling 
to  such  a  degree  as  to  be  badly  injured  as  to 
their  germinating  qualities.  It  is  well  known 
that  nuts,  which  are  destined  for  propagation, 
are  as  a  rule  not  allowed  to  fall  off,  but  are 
taken  from  the  trees  with  great  care. 

Summing  up  his  arguments,  Cook  concludes 
that  there  is  little  in  the  way  of  known  facts 
to  support  the  poetic  theory  of  the  coconut- 
palm  dropping  its  fruits  into  the  sea  to  float 
away  to  barren  islands  and  prepare  them  for 


Cultivated  Elementary  Species  87 

human  habitation.  Shipwrecks  might  furnish 
a  successful  method  of  launching  viable  coco- 
nuts, and  such  have  no  doubt  sometimes  con- 
tributed to  their  distribution.  But  this  as- 
sumption implies  a  dissemination  of  the  nuts  by 
man,  and  if  this  principal  fact  is  granted,  it  is 
far  more  natural  to  believe  in  a  conscious  in- 
telligent dissemination. 

The  coconut  is  a  cultivated  tree.  It  may  be 
met  with  in  some  spots  distant  from  human 
dwellings,  but  whenever  such  cases  have  been 
subjected  to  a  closer  scrutiny,  it  appears  that 
evidently,  or  at  least  probably,  huts  had  for- 
merly existed  in  their  neighborhood,  but  having 
been  destroyed  by  some  accident,  had  left  the 
palm  trees  uninjured.  Even  in  South  America, 
where  it  may  be  found  in  forests  at  great  dis- 
tances from  the  sea-shore,  it  is  not  at  all  certain 
that  true  native  localities  occur,  and  it  seems  to 
be  quite  lost  in  its  natural  condition. 

Granting  the  cultivated  state  of  the  palms  as 
the  only  really  important  one,  and  considering 
the  impossibility  or  at  least  great  improbability 
of  its  dissemination  by  natural  means,  the  dis- 
tribution by  man  himself,  according  to  his 
wants,  assumes  the  rank  of  an  hypothesis  fully 
adequate  to  the  explanation  of  all  the  facts  con- 
cerning the  life-history  of  the  tree. 

We  now  have  to  inquire  into  the  main  ques- 


88  Elementary  Species 

tioD,  whether  it  is  probable  that  the  coconut  is 
of  American  or  of  Asiatic  origin,  leaving  aside 
the  historic  evidence  which  goes  to  prove  that 
nothing  is  known  about  the  period  in  which  its 
dissemination  from  one  hemisphere  to  another 
took  place,  we  will  now  consider  only  the  bo- 
tanic and  geographic  evidence,  brought  forward 
by  Cook.  He  states  that  the  whole  family  of 
coconut-palms,  consisting  of  about  20  genera 
and  200  species,  are  all  strictly  American  with 
the  exception  of  the  rather  aberrant  African  oil- 
palm,  which  has,  however,  an  American  relative 
referred  to  the  same  genus.  The  coconut  is 
the  sole  representative  of  this  group  which  is 
connected  with  Asia  and  the  Malayan  region,  but 
there  is  no  manifest  reason  why  other  members 
of  the  same  group  could  not  have  established 
themselves  there,  and  maintained  an  existence 
under  conditions,  which  are  not  at  all  unfavor- 
able to  them.  The  only  obvious  reason  is  the 
assumption  already  made,  that  the  distribution 
was  brought  about  by  man,  and  thus  only  af- 
fected the  species,  chosen  by  him  for  cultiva- 
tion. That  the  coconut  cannot  have  been  im- 
ported from  Asia  into  America  seems  to  be  the 
most  obvious  conclusion  from  the  arguments 
given.  It  should  be  briefly  noted,  that  it  was 
known  and  widely  distributed  in  tropical  Amer- 
ica at  the  time  of  the  discovery  of  that  continent 


I 


Cultivated  Elementary  Species  89 

by  Columbus,  according  to  accounts  of  Oviedo 
and  other  contemporary  Spanish  writers. 

Concluding  we  may  state  that  according  to 
the  whole  evidence  as  it  has  been  discussed  by 
De  Candolle  and  especially  by  Cook,  the  coco- 
nut-palm is  of  American  origin  and  has  been  dis- 
tributed as  a  cultivated  tree  by  man  through  the 
whole  of  its  wide  range.  This  must  have  hap- 
pened in  a  prehistoric  era,  thus  affording  time 
enough  for  the  subsequent  development  of  the 
fifty  and  more  known  varieties.  But  the  pos- 
sibility that  at  least  some  of  them  have  origin- 
ated before  culture  and  have  been  deliberately 
chosen  by  man  for  distribution,  of  course  re- 
mains unsettled. 

Coconuts  are  not  very  well  adapted  for 
natural  dispersal  on  land,  and  this  would  rather 
induce  us  to  suppose  an  origin  within  the  period 
of  cultivation  for  the  whole  group.  There  are 
a  large  number  of  cultivated  varieties  of  differ- 
ent species  which  by  some  peculiarity  do  not 
seem  adapted  for  the  conditions  of  life  in  the 
wild  state.  These  last  have  often  been  used  to 
prove  the  origin  of  varietal  forms  during  cul- 
ture. One  of  the  oldest  instances  is  the  variety 
or  rather  subspecies  of  the  opium-poppy,  which 
lacks  the  ability  to  burst  open  its  capsules.  The 
seeds,  which  are  thrown  out  by  the  wind,  in  the 
common  forms,  through  the  apertures  under- 


90  Elementary  Species 

neath  the  stigma,  remain  enclosed.  This  is 
manifestly  a  very  useful  adaption  for  a  culti- 
vated plant,  as  by  this  means  no  seeds  are  lost. 
It  would  be  quite  a  disadvantage  for  a  wild 
species,  and  is  therefore  claimed  to  have  been 
connected  from  the  beginning  with  the  culti- 
vated form. 

The  large  kernels  of  corn  and  grain,  of  beans 
and  peas,  and  even  of  the  lupines  were  consid- 
ered by  Darwin  and  others  to  be  unable  to  cope 
with  natural  conditions  of  life.  Many  valuable 
fruits  are  quite  sterile,  or  produce  extremely 
few  seeds.  This  is  notoriously  the  case  with 
some  of  the  best  pears  and  grapes,  with  the 
pine-apples,  bananas,  bread-fruits,  pomegran- 
ate and  some  members  of  the  orange  tribe.  It 
is  open  to  discussion  as  to  what  may  be  the  im- 
mediate cause  of  this  sterility,  but  it  is  quite 
evident,  that  all  such  sterile  varieties  must  have 
originated  in  a  cultivated  condition.  Otherwise 
they  would  surely  have  been  lost. 

In  horticulture  and  agriculture  the  fact  that 
new  varieties  arise  from  time  to  time  is  beyond 
all  doubt,  and  it  is  not  this  question  with  which 
we  are  now  concerned.  Our  arguments  were 
only  intended  to  prove  that  cultivated  species, 
as  a  rule,  are  derived  from  wild  species,  which 
obey  the  laws  discussed  in  a  previous  lecture. 
The  botanic  units  are  compound  entities,  and 


Cultivated  Elementary  Species  91 

the  real  systematic  units  in  elementary  species 
play  tlie  same  part  as  in  ordinary  wild  species. 
The  inference  that  the  origin  of  the  cultivated 
plants  is  multiple,  in  most  cases,  and  that  more 
than  one,  often  many  separate  elementary 
forms  of  the  same  species  must  originally  have 
been  taken  into  cultivation,  throws  much  light 
upon  man}^  highly  important  problems  of  culti- 
vation and  selection.  This  aspect  of  the  ques- 
tion will  therefore  be  the  subject  of  the  next 
lecture. 


f 


Lecture  IV 

SELECTION    OF   ELEMENTARY   SPECIES 

The  improvement  of  cultivated  plants  must 
obviously  begin  with  already  existing  forms. 
This  is  true  of  old  cultivated  sorts  as  well  as  for 
recent  introductions.  In  either  case  the  start- 
ing-point is  as  important  as  the  improvement, 
or  rather  the  results  depend  in  a  far  higher  de- 
gree on  the  adequate  choice  of  the  initial  ma- 
terial than  on  the  methodical  and  careful  treat- 
ment of  the  chosen  varieties.  This  however, 
has  not  always  been  appreciated  as  it  deserves, 
nor  is  its  importance  at  present  universally 
recognized.  The  method  of  selecting  plants  for 
the  improvement  of  the  race  was  discovered  by 
Louis  Vilmorin  about  the  middle  of  the  last 
century.  Before  his  time  selection  was  ap- 
plied to  domestic  animals,  but  Vilmorin  was  the 
first  to  apply  this  principle  to  plants.  As  is 
well  known,  he  used  this  method  to  increase 
the  amount  of  sugar  in  beets  and  thus  to  raise 
their  value  as  forage-crops,  with  such  success, 
that  his  plants  have  since  been  used  for  the  pro- 

92 


Selection  of  Elementary  Species         93 

duction  of  sugar.  He  must  have  made  some 
choice  among  the  numerous  available  sorts  of 
beets,  or  chance  must  have  placed  in  his  hands 
one  of  the  most  appropriate  forms.  On  this 
point  however,  no  evidence  is  at  hand. 

Since  the  work  of  Vilmorin  the  selection-prin- 
ciple has  increased  enormously  in  importance, 
for  practical  purposes  as  well  as  for  the  the- 
oretical aspect  of  the  subject.  It  is  now  being 
applied  on  a  large  scale  to  nearly  all  ornamental 
plants.  It  is  the  one  great  principle  now  in 
universal  practice  as  well  as  one  of  preeminent 
scientific  value.  Of  course,  the  main  argu- 
ments of  the  evolution  theory  rest  upon  mor- 
phologic, systematic,  geographic  and  pale- 
ontologic  evidence.  But  the  question  as  to  how 
we  can  coordinate  the  relation  between 
existing  species  and  their  supposed  ancestors 
is  of  course  one  of  a  physiologic  nature.  Di- 
rect observation  or  experiments  were  not  avail- 
able for  Darwin  and  so  he  found  himself  con- 
strained to  make  use  of  the  experience  of  breed- 
ers. This  he  did  on  a  broad  scale,  and  with 
such  success  that  it  was  precisely  this  side  of 
his  arguments  that  played  the  major  part  in 
convincing  his  contemporaries. 

The  work  of  the  breeders  previous  to  Dar- 
win's time  had  not  been  very  critically  per- 
formed.    Recent  analvses  of  the  evidence  ob- 


94  Elementary  Species 

tained  from  them  show  that  nmnerous  types 
of  variability  were  usually  thrown  together. 
What  type  in  each  case  afforded  the  material, 
which  the  breeder  in  reality  made  use  of,  has 
only  been  inquired  into  in  the  last  few  decades. 
Among  those  who  have  opened  the  way  for 
thorough  and  more  scientific  treatment  are  to 
be  mentioned  Rimpau  and  Von  Riimker  of  Ger- 
many and  W.  M.  Hays  of  America. 

Von  Riimker  is  to  be  considered  as  the  first 
writer,  who  sharply  distinguished  between  two 
phases  of  methodical  breeding-selection.  One 
side  he  calls  the  production  of  new  forms,  the 
other  the  improvement  of  the  breed.  He  dealt 
with  both  methods  extensively.  New  forms  are 
considered  as  spontaneous  variations  occurring 
or  originating  without  human  aid.  They  have 
only  to  be  selected  and  isolated,  and  their 
progeny  at  once  yields  a  constant  and  pure  race. 
This  race  retains  its  character  as  long  as  it  is 
protected  against  the  admixture  of  other  minor 
varieties,  either  by  cross-pollination,  or  by  ac- 
cidental seeds. 

Improvement,  on  the  other  hand,  is  the  work 
of  man.  New  varieties  of  course  can  only  be 
isolated  if  chance  offers  them;  the  improve- 
ment is  not  incumbent  on  chance.  It  does  not 
create  really  anything  new,  but  develops  char- 
acters, which  were  already  existing.     It  brings 


Selection  of  Elementary  Species         95 

the  race  above  its  average,  and  must  guard 
constantly  against  the  regression  towards  this 
average  which  usually  takes  place. 

Hays  has  repeatedly  insisted  upon  the  prin- 
ciple of  the  choice  of  the  most  favorable  varie- 
ties as  the  foundation  for  all  experiments  in 
improving  races.  He  asserts  that  half  the  bat- 
tle is  won  by  choosing  the  variety  which  is  to 
serve  as  a  foundation  stock,  while  the  other  half 
depends  upon  the  selection  of  parent-plants 
within  the  chosen  variety.  Thus  the  choice  of 
the  variety  is  the  first  principle  to  be  applied  in 
every  single  case;  the  so-called  artificial  selec- 
tion takes  only  a  secondary  place.  Calling  all 
minor  units  within  the  botanic  species  by  the 
common  name  of  varieties,  without  regard  to 
the  distinction  between  elementary  species  and 
retrograde  varieties,  the  principle  is  designated 
by  the  term  of  '^  variety-testing."  This  test- 
ing of  varieties  is  now,  as  is  universally  known, 
one  of  the  most  important  lines  of  work  of  the 
agricultural  experiment  stations.  Every  state 
and  every  region,  in  some  instances  even  the 
larger  farms,  require  a  separate  variety  of 
corn,  or  wheat,  or  other  crops.  They  must  be 
segregated  from  among  the  hundreds  of  gen- 
erally cultivated  forms,  within  each  single  bo- 
tanic species.  Once  found,  the  type  may  be 
ameliorated  according  to  the  local  conditions 


96  Elementary  Species 

and  needs,  and  this  is  a  question  of  improve- 
ment. 

The  fact  that  our  cultivated  plants  are  com- 
monly mixtures  of  different  sorts,  has  not  al- 
\rays  been  known.  The  first  to  recognize  it  seems 
to  have  been  the  Spanish  professor  of  botany, 
Mariano  Lagasca,  who  published  a  number  of 
Spanish  papers  dealing  with  useful  plants  and 
botanical  subjects  between  1810  and  1830, 
among  them  a  catalogue  of  plants  cultivated  in 
the  Madrid  Botanical  Garden.  Once  when  he 
was  on  a  visit  to  Colonel  Le  Couteur  on  his  farm 
in  Jersey,  one  of  the  Channel  Islands  off  the 
coast  of  France,  in  discussing  the  value  of  the 
fields  of  wheat,  he  pointed  out  to  his  host,  that 
they  were  not  really  pure  and  uniform,  as  was 
thought  at  that  time,  and  suggested  the  idea 
that  some  of  the  constituents  might  form  a 
larger  part  in  the  harvest  than  others.  In  a 
single  field  he  succeeded  in  distinguishing  no 
less  than  23  varieties,  all  growing  together. 
Colonel  Le  Couteur  took  the  hint,  and  saved  the 
seeds  of  a  single  plant  of  each  supposed  va- 
riety separatel}^  These  he  cultivated  and  mul- 
tiplied till  he  got  large  lots  of  each  and  could 
compare  their  value.  From  among  them  he 
then  chose  the  variety  producing  the  greatest 
amount  of  the  finest,  whitest  and  most  nu- 
tritious flour.     This  he  eventually  placed  in  the 


Selection  of  Elementary  Species         97 

market  under  the  naiae  of  "  Talavera  de 
Bellevue. "  It  is  a  tall,  white  variety,  with  long 
and  slender  white  heads,  almost  without  awns, 
and  with  fine  white  pointed  kernels.  It  was  in- 
troduced into  commerce  about  1830,  and  is  still 
one  of  the  most  generally  cultivated  French 
wheats.  It  was  highly  prized  in  the  magnifi- 
cent collection  of  drawings  and  descriptions  of 
wheats,  published  by  Vilmorin  under  the  title 
''  Les  meilleurs  bles  "  and  is  said  to  have  quite 
a  number  of  valuable  qualities,  branching  freely 
and  producing  an  abundance  of  good  grain  and 
straw.  It  is  however,  sensitive  to  cold  win- 
ters in  some  degree  and  thereby  limited  in  its 
distribution.  Hallett,  the  celebrated  English 
wheat-breeder,  tried  in  vain  to  improve  the 
peculiar  qualities  of  this  valuable  production 
of  Le  Couteur's. 

Le  Couteur  worked  during  many  years  along 
this  line,  long  before  the  time  when  Vilmorin 
conceived  the  idea  of  improvement  by  race- 
selections,  and  he  used  only  the  simple 
principle  of  distinguishing  and  isolating  the 
members  of  his  different  fields.  Later  he  pub- 
lished his  results  in  a  work  on  the  varieties, 
peculiarities  and  classification  of  wheat  (1843), 
which  though  now  very  rare,  has  been  the  basis 
and  origin  of  the  principle  of  variety-testing. 

The  discoverv  of  Lagasca  and  Le  Couteur  was 


98  Elementary  Species 

of  course  not  applicable  to  the  wheat  of  Jersey 
alone.  The  common  cultivated  sorts  of  wheat 
and  other  grains  were  mixtures  then  as  they 
are  even  now.  Improved  varieties  are,  or  at 
least  should  be,  in  most  cases  pure  and  uniform, 
but  ordinary  sorts,  as  a  rule,  are  mixtures. 
Wheat,  barley  and  oats  are  self-fertile  and  do 
not  mix  in  the  field  through  cross-pollination. 
Every  member  of  the  assemblage  propagates  it- 
self, and  is  only  checked  by  its  own  greater  or 
less  adaptation  to  the  given  conditions  of  life. 
Eimpau  has  dealt  at  large  with  the  phenomenon 
as  it  occurs  in  the  northern  and  middle  parts  of 
Germany.  Even  Rivett's  ^'  Bearded  wheat," 
which  was  introduced  from  England  as  a  fine 
improved  variety,  and  has  become  widely  dis- 
tributed throughout  Germany,  cannot  keep  it- 
self pure.  It  is  found  mingled  almost  any- 
where with  the  old  local  varieties,  which  it  was 
destined  to  supplant.  Any  lot  of  seed  ex- 
hibits such  impurities,  as  I  have  had  the  op- 
portunity of  observing  myself  in  sowings  in 
the  experimental-garden.  But  the  impurities 
are  only  mixtures,  and  all  the  plants  of 
Rivett's  ^^  Bearded  wheat,"  which  of  course 
constitute  the  large  majority,  are  of  pure  blood. 
This  may  be  confirmed  when  the  seeds  are  col- 
lected and  sown  separately  in  cultures  that  can 
be  carefully  guarded. 


Selection  of  Elementary  Species  99 

In  order  to  get  a  closer  insiglit  into  the 
causes  of  this  confused  condition  of  ordinarj^ 
races,  Rimpau  made  some  observations  on 
Rivett's  wheat.  He  found  that  it  suffers  from 
frost  during  winter  more  than  the  local  Ger- 
man varieties,  and  that  from  various  causes, 
alien  seeds  may  accidentally,  and  not  rarely, 
become  mixed  with  it.  The  threshing-machines 
are  not  always  as  clean  as  they  should  be  and 
may  be  the  cause  of  an  accidental  mixture. 
The  manure  comes  from  stables,  where  straw 
and  the  dust  from  many  varieties  are  thrown 
together,  and  consequently  living  kernels 
may  become  mixed  with  the  dung.  Such  stray 
grains  will  easily  germinate  in  the  fields,  where 
they  find  more  congenial  conditions  than  does 
the  improved  variety.  If  winter  arrives  and 
kills  quantities  of  this  latter,  the  accidental  local 
races  will  find  ample  space  to  develop.  Once 
started,  they  will  be  able  to  multiply  so  rapidly, 
that  in  one  or  two  following  generations  they 
will  constitute  a  very  considerable  portion  of 
the  whole  harvest.  In  this  way  the  awnless 
German  wheat  often  prevails  over  the  intro- 
duced English  variety,  if  the  latter  is  not  kept 
pure  by  continuous  selection. 

The  Swiss  wheat-breeder  Risler  made  an  ex- 
periment which  goes  to  prove  the  certainty  of 
the    explanation    given    by    Rimpau.     He    ob- 


100  Elementary  Species 

served  on  his  farm  at  Saleves  near  the  lake  of 
Geneva  that  after  a  lapse  of  time  the  ' '  Galland- 
wheat  '  ^  deteriorated  and  assumed,  as  was  gen- 
erally believed,  the  characters  of  the  local  sorts. 
In  order  to  ascertain  the  real  cause  of  this  ap- 
parent change,  he  sowed  in  alternate  rows  in  a 
field,  the  '*  Galland  "  and  one  of  the  local  va- 
rieties. The  ^'  Galland  "  is  a  race  with  ob- 
vious characters  and  was  easily  distinguished 
from  the  other  at  the  time  when  the  heads  were 
ripe.  They  are  bearded  when  flowering,  but 
afterwards  throw  off  the  awns.  The  kernels 
are  very  large  and  yield  an  extraordinarily 
good,  white  flour. 

During  the  first  summer  all  the  heads  of  the 
"  Galland  "  rows  had  the  deciduous  awns  but 
the  following  year  these  were  only  seen  on  half 
of  the  plants,  the  remainder  having  smooth 
heads,  and  the  third  vear  the  ''  Galland  "  had 
nearly  disappeared,  being  supplanted  by  the 
competing  local  race.  The  cause  of  this  rapid 
change  was  found  to  be  twofold.  First  the 
'^  Galland,"  as  an  improved  variety,  suffers 
from  the  winter  in  a  far  higher  degree  than  the 
native  Swiss  sorts,  and  secondly  it  ripens  its 
kernels  one  or  two  weeks  later.  At  the  time  of 
harvest  it  may  not  have  become  fully  ripe,  while 
the  varieties  mixed  with  it  had  reached  maturity. 

The  wild  oat,  Avena  fatua,  is  very  common  in 


JL 


Selection  of  Elementary  Species       101 

Europe  from  whence  it  has  been  introduced  in 
the  United  States.  In  summers  which  are  un- 
favorable to  the  development  of  the  cultivated 
oats  it  may  be  observed  to  multiply  with  an  al- 
most incredible  rapidity.  It  does  not  contrib- 
ute to  the  harvest,  and  is  quite  useless.  If  no 
selection  were  made,  or  if  selection  were  dis- 
continued, it  would  readily  supplant  the  culti- 
vated varieties. 

From  these  several  observations  and  experi- 
ments it  may  be  seen,  that  it  is  not  at  all  easy 
to  keep  the  common  varieties  of  cereals  pure 
and  that  even  the  best  are  subject  to  the  en- 
croachment of  impurities.  Hence  it  is  only 
natural  that  races  of  cereals,  when  cultivated 
without  the  utmost  care,  or  even  when  selected 
without  an  exact  knowledge  of  their  single  con- 
stituents, are  always  observed  to  be  more  or 
less  in  a  mixed  condition.  Here,  as  everywhere 
with  cultivated  and  wild  plants,  the  systematic 
species  consist  of  a  number  of  minor  types, 
which  pertain  to  different  countries  and  cli- 
mates, and  are  growing  together  in  the  same 
climate  and  under  the  same  external  conditions. 
They  do  not  mingle,  nor  are  their  differentiat- 
ing characters  destroyed  by  intercrossing. 
They  each  remain  pure,  and  may  be  isolated 
whenever  and  wherever  the  desirability  for 
such  a  proceeding  should  arise.     The  purity  of 


102  Elementary  Species 

the  races  is  a  condition  implanted  in  them  by 
man,  and  nature  always  strives  against  this 
arbitrary  and  one-sided  improvement.  Numer- 
ous slight  differences  in  characters  and  numer- 
ous external  influences  benefit  the  minor  types 
and  bring  them  into  competition  with  the  better 
ones.  Sometimes  they  tend  to  supplant  the 
latter  wholly,  but  ordinarily  sooner  or  later  a 
state  of  equilibrium  is  reached,  in  which  hence- 
forth the  different  sorts  may  live  together. 
Some  are  favored  by  warm  and  others  by  cool 
summers,  some  are  injured  by  hard  winters, 
while  others  thrive  then  and  are  therefore  rela- 
tively at  an  advantage.  The  mixed  condition 
is  the  rule,  purity  is  the  exception. 

Different  sorts  of  cereals  are  not  always 
easily  distinguishable  by  the  layman  and  there- 
fore I  will  draw  your  attention  to  conditions  in 
meadows,  where  a  corresponding  phenomenon 
can  be  observed  in  a  much  simpler  way. 

Only  artificial  pasture-grounds  are  seen  to 
consist  of  a  single  species  of  grass  or  clover. 
The  natural  condition  in  meadows  is  the  occur- 
rence of  clumps  of  grasses  and  some  clovers, 
mixed  up  with  perhaps  twenty  or  more  species 
of  other  genera  and  families.  The  numerical 
proportion  of  these  constituents  is  of  great  in- 
terest, and  has  been  studied  at  Rothamstead  in 
England  and  on  a  number  of  other  farms.     It  is 


Selection  of  Elementary  Species       103 

always  changing.  No  two  successive  years  show 
exactly  the  same  proportions.  At  one  time  one 
species  prevails,  at  another  time  one  or  two  or 
more  other  species.  The  weather  during  the 
spring  and  summer  benefits  some  and  hurts 
others,  the  winter  may  be  too  cold  for  some,  but 
again  harmless  for  others,  the  rainfall  may 
partly  drown  some  species,  while  others  re- 
main uninjured.  Some  weeds  may  be  seen  flow- 
ering profusely  during  some  years,  while  in 
other  summers  they  are  scarcely  to  be  found  in 
the  same  meadow.  The  whole  population  is  in  a 
fluctuating  state,  some  thriving  and  others  de- 
teriorating. It  is  a  continuous  response  to  the 
ever  changing  conditions  of  the  weather.  Rare- 
ly a  species  is  wholly  annihilated,  though  it 
may  apparently  be  so  for  years ;  but  either  from 
seeds  or  from  rootstocks,  or  even  from  neigh- 
boring lands,  it  may  sooner  or  later  regain  its 
foothold  in  the  general  struggle  for  life. 

This  phenomenon  is  a  very  curious  and  in- 
teresting one.  The  struggle  for  life,  which 
plays  so  considerable  a  part  in  the  modern 
theories  of  evolution,  may  be  seen  directly  at 
work.  It  does  not  alter  the  species  themselves, 
as  is  commonly  supposed,  but  it  is  always 
changing  their  numerical  proportion.  Any 
lasting  change  in  the  external  conditions  will  of 
course  alter  the  average  oscillation  and  the  in- 


104  Elementary  Species 

tiuence  of  such  alterations  will  manifest  itself 
in  most  cases  simply  in  new  numerical  propor- 
tions. Only  extremes  have  extreme  effects,  and 
the  chance  for  the  weaker  sorts  to  be  complete- 
ly overthrown  is  therefore  very  small. 

Any  one,  who  has  the  opportunity  of  observ- 
ing a  waste  field  during  a  series  of  years,  should 
make  notes  concerning  the  numerical  propor- 
tions of  its  inhabitants.  Exact  figures  are  not 
at  all  required;  approximate  estimates  will  or- 
dinarily prove  to  be  sufficient,  if  only  the  stand- 
ard remains  the  same  during  the  succeeding 
years. 

The  entire  mass  of  historic  evidence  goes  to 
prove  that  the  same  conditions  have  always 
prevailed,  from  the  very  beginning  of  cultiva- 
tion up  to  the  present  time.  The  origin  of 
the  cultivation  of  cereals  is  to  be  sought  in  cen- 
tral Asia.  The  recent  researches  of  Solms- 
Laubach  show  it  to  be  highly  probable  that  the 
historic  origin  of  the  wheat  cultivated  in  China, 
is  the  same  as  that  of  the  wheat  of  Eg}^pt  and 
Europe.  Remains  of  cereals  are  found  in  the 
graves  of  Egyptian  mummies,  in  the  mounds 
of  waste  material  of  the  lake-dwellings  of  Cen- 
tral Europe,  and  figures  of  cereals  are  to  be 
seen  on  old  Roman  coins.  In  the  sepulchre  of 
King  Ra-n-Woser  of  the  Fifth  Dynasty  of 
Egypt,  who  lived  about  2000  years  B.  C,  two 


Selection  of  Elementary  Species       105 

tombs  have  recently  been  opened  by  the  Ger- 
man Oriental  Society.  In  them  were  found 
quantities  of  the  tares  of  the  Triticum  dicoccum, 
one  of  the  more  primitive  forms  of  wheat.  In 
other  temples  and  pyramids  and  among  the 
stones  of  the  walls  of  Dashur  and  El  Kab 
studied  by  linger,  different  species  and  varie- 
ties of  cereals  were  discovered  in  large  quan- 
tities, that  showed  their  identity  with  the  pres- 
ent prevailing  cultivated  races  of  Egypt. 

The  inhabitants  of  the  lake-dwellings  in 
Switzerland  possessed  some  varieties  of  cereals, 
which  have  entirely  disappeared.  They  are 
distinguished  by  Heer  under  special  names. 
The  small  barley  and  the  small  wheat  of  the 
lake-dwellers  are  among  them.  All  in  all  there 
were  ten  well  distinguished  varieties  of  cereals, 
the  Panicum  and  the  Setaria  or  millet  being  of 
the  number.  Oats  were  evidently  introduced 
only  toward  the  very  last  of  the  lake-dwelling 
period,  and  rye  is  of  far  later  introduction  into 
western  Europe.  Similar  results  are  attained 
by  the  examination  of  the  cereals  figured  by  the 
Romans  of  the  same  period. 

All  these  are  archaeologic  facts,  and  give  but 
slight  indications  concerning  the  methods  of 
cultivation  or  the  real  condition  of  the  culti- 
vated races  of  that  time.  Virgil  has  left  us 
some  knowledge  of  the  requirements  of  method- 


106  Elementary  Species 

ical  culture  of  cereals  of  his  time.    In  his  poem 
Georgics  (I.  197)  the  following  lines  are  found: 

Vidi  lecta  diu,  et  multo  spectata  labore 
Degenerare  tamen,  ni  vis  humana  quotannis 
Maxima  quaeque  manu  legeret. 
(The  chosen  seed,  through  years  and  labor 

improved, 
Was  seen  to  run  back,  unless  yearly 
Man  selected  by  hand  the  largest  and  fullest 
of  ears.) 

Elsewhere  Virgil  and  also  some  lines  of 
Columella  and  Varro  go  to  prove  in  the  same 
way  that  selection  was  applied  by  the  Romans 
to  their  cereals,  and  that  it  was  absolutely 
necessary  to  keep  their  races  pure.  There  is 
little  doubt,  but  that  it  was  the  same  principle 
as  that  which  has  led,  after  many  centuries,  to 
the  complete  isolation  and  improvement  of  the 
very  best  races  of  the  mixed  varieties.  It  fur- 
ther proves  that  the  mixed  conditions  of  the 
cereals  was  known  to  man  at  that  time,  al- 
though distinct  ideas  of  specific  marks  and  dif- 
ferences were  of  course  still  wholly  lacking.  It 
is  proof  also  that  cultivated  cereals  from  the 
earliest  times  must  have  been  built  up  of  num- 
erous elementary  forms.  Moreover  it  is  very 
probable,  that  in  the  lapse  of  centuries  a  good- 
ly  number   of   such   types   must   have    disap- 


Selection  of  Elementary  Species       107 

peared.  Among  the  vanished  forms  are  the 
special  barley  and  wheat  of  the  lake-dwellings, 
the  remains  of  which  have  been  accidentally 
preserved,  but  most  of  the  forms  must  have  dis- 
appeared without  leaving  any  trace. 

This  inference  is  supported  by  the  researches 
of  Solms-Laubach,  who  found  that  in  Abyssinia 
numerous  primitive  types  of  cereals  are  still  in 
culture.  They  are  not  adequate  to  compete 
with  our  present  varieties,  and  would  no  doubt 
also  have  disappeared,  had  they  not  been  pre- 
served by  such  quite  accidental  and  almost 
primitive  isolation. 

Closing  this  somewhat  long  digression  into 
history  we  will  now  resume  our  discussion  con- 
cerning the  origin  of  the  method  of  selecting 
cereals  for  isolation  and  segregate-cultivation. 
Some  decades  after  Le  Couteur,  this  method 
was  taken  up  by  the  celebrated  breeder  Patrick 
Sheriff  of  Haddington  in  Scotland.  His  be- 
lief, which  was  general  at  that  time,  was  ^^  That 
cultivation  has  not  been  found  to  change  well 
defined  kinds,  and  that  improvement  can  be  best 
attained  by  selecting  new  and  superior  varie- 
ties, which  nature  occasionally  produces,  as  if 
inviting  the  husbandman  to  stretch  forth  his 
hand  and  cultivate  them." 

Before  going  into  the  details  of  Sheriff's 
work  it  is  as  well  to  say  something  concerning 


108  Elementary  Species 

* 

the  use  of  the  word  "  selection."  This  word 
was  used  by  Sheriff  as  seen  in  the  quotation 
given,  and  it  was  obviously  designed  to  convey 
the  same  idea  as  the  word  ''  lecta  "  in  the  quo- 
tation from  Virgil.  It  was  a  choice  of  the  best 
plants  from  among  known  mixed  fields,  but  the 
chosen  individuals  were  considered  to  be  repre- 
sentatives of  pure  and  constant  races,  which 
could  only  be  isolated,  but  not  ameliorated. 
Selection  therefore,  in  the  primitive  sense  of 
the  word,  is  the  choice  of  elementary  species 
and  varieties,  with  no  other  purpose  than  that 
of  keeping  them  as  pure  as  possible  from  the 
admixture  of  minor  sorts.  The  E-omans  at- 
tained this  end  only  imperfectly,  simply  be- 
cause the  laws  governing  the  struggle  for  life 
and  the  competition  of  numerous  sorts  in  the 
fields  were  unsuspected  by  them. 

Le  Couteur  and  Sheriff  succeeded  in  the  solu- 
tion of  the  problem,  because  they  had  discovered 
the  importance  of  isolation.  The  combination 
of  a  careful  choice  with  subsequent  isolation 
was  all  they  knew  about  it,  and  it  was  one  of 
the  great  achievements  to  which  modern  agri- 
culture owes  its  success. 

The  other  great  principle  was  that  of  Vil- 
morin.  It  was  the  improvement  within  the 
race,  or  the  ''  amelioration  of  the  race  "  as  it 
was  termed  by  him.     It  was  introduced  into 


Selection  of  Elementary  Species       109 

England  by  F.  F.  Hallett  of  Brighton  in  Sussex, 
who  at  once  called  it  ''  pedigree-culture,"  and 
produced  his  first  new  variety  under  the  very 
name  of  ''  Pedigree-wheat."  This  principle, 
which  yields  improved  strains,  that  are  not  con- 
stant but  dependent  on  the  continued  and  care- 
ful choice  of  the  best  plants  in  each  succeeding 
generation,  is  now  generally  called  '^  selec- 
tion." But  it  should  always  be  remembered 
that  according  to  the  historic  evolution  of  the 
idea,  the  word  has  the  double  significance  of  the 
distinction  and  isolation  of  constant  races  from 
mixtures,  and  that  of  the  choice  of  the  best  rep- 
resentatives of  a  race  during  all  the  years  of  its 
existence.  Even  sugar-beets,  the  oldest  ^^  se- 
lected ' '  agricultural  plants  are  far  from  having 
freed  themselves  from  the  necessity  of  contin- 
uous improvement.  Without  this  they  would 
not  remain  constant,  but  would  retrograde  with 
great  rapidity. 

The  double  meaning  of  the  word  selection 
still  prevailed  when  Darwin  published  his 
<<  Origin  of  Species."  This  was  in  the  year 
1859,  and  at  that  time  Shirreff  was  the  highest 
authority  and  the  most  successful  breeder  of 
cereals.  Vilmorin's  method  had  been  applied 
only  to  beets,  and  Hallett  had  commenced  his 
pedigree-cultures  only  a  few  years  before  and 
his  first  publication  of  the  ^^  Pedigree-wheat  " 


110  Elementary  Species 

appeared  some  years  later  at  the  International  | 

Exhibition  of  London  in  1862.     Hence,  when- 
ever Darwin  speaks  of  selection,  Shirreif 's  use  i 
of  the  word  mav  as  well  be  meant  as  that  of 
Vilmorin. 

However,  before  going  deeper  into  such  the- 
oretical questions,  we  will  first  consider  the 
facts,  as  given  by  Shirretf  himself. 

During  the  best  part  of  his  life,  in  fact  during 
the  largest  part  of  the  first  half  of  the  nine- 
teenth centurj^  Shirretf  worked  according  to  a 
very  simple  principle.  When  quite  young  he 
had  noticed  that  sometimes  single  plants  having 
better  qualities  than  the  average  were  seen 
in  the  fields.  He  saved  the  grains,  or  some- 
times the  whole  heads  of  such  plants  separate- 
ly, and  tried  to  multiply  them  in  such  man- 
ner as  to  avoid  intermixtures. 

His  first  result  was  the  ''  Mungoswell's 
wheat.''  In  the  spring  of  1819  he  observed 
quite  accidentally  in  a  field  of  the  farm  of  that 
name,  a  single  plant  which  attracted  his  atten- 
tion by  a  deeper  green  and  by  being  more  heav- 
ily headed  out.  Without  going  into  further  de- 
tails, he  at  once  chose  this  specimen  as  the  start- 
ing point  -of  a  new  race.  He  destroyed  the  sur- 
rounding plants  so  as  to  give  it  more  space,  ap- 
plied manure  to  its  roots,  and  tended  it  with 
special  care.     It  yielded  63  heads  and  nearly 


Selection  of  Elementary  Species       111 

2500  grains.  All  of  these  were  sown  the  fol- 
lowing fall,  and  likewise  in  the  succeeding  years 
the  whole  harvest  was  sown  in  separate  lots. 
After  two  years  of  rapid  multiplication  it 
proved  to  be  a  good  new  variety  and  was 
brought  into  commerce.  It  has  become  one  of 
the  prominent  varieties  of  wheat  in  East 
Lothian,  that  county  of  Scotland  of  which  Had- 
dington is  the  principal  borough. 

The  grains  of  ''  Mungoswell's  wheat  "  are 
whiter  than  those  of  the  allied  ''  Hunter's 
wheat,"  more  rounded  but  otherwise  of  the 
same  size  and  weight.  The  straw  is  taller  and 
stronger,  and  each  plant  produces  more  culms 
and  more  heads. 

Shirreff  assumed,  that  the  original  plant  of 
this  variety  was  a  sport  from  the  race  in  which 
he  had  found  it,  and  that  it  was  the  only  in- 
stance of  this  sport.  He  gives  no  details 
about  this  most  interesting  side  of  the  question, 
omitting  even  to  tell  the  name  of  the  parent- 
variety.  He  only  asserts  that  it  was  seen  to  be 
better,  and  afterwards  proved  so  by  the  appre- 
ciation of  other  breeders  and  its  success  in 
trade.  He  observed  it  to  be  quite  constant 
from  the  beginning,  no  subsequent  selection  be- 
ing needed.  This  important  feature  was  simp- 
ly assumed  by  him  to  be  true  as  a  matter  of 
course. 


112  Elementary  Species 

Some  years  afterwards,  in  the  smimier  of 
1824,  he  observed  a  large  specimen  of  oats 
in  one  of  the  fields  of  the  same  farm.  Being 
at  that  time  occupied  in  making  a  standard  col- 
lection of  oats  for  a  closer  comparison  of  the 
varieties,  he  saved  the  seeds  of  that  plant  and 
sowed  them  in  a  row  in  his  experiment-field. 
It  yielded  the  largest  culms  of  the  whole  collec- 
tion and  bore  long  and  heavy  kernels  with  a  red 
streak  on  the  concave  side  and  it  excelled  all 
other  sorts  by  the  fine  qualities  of  its  very  white 
meal.  In  the  unequal  length  of  its  stalks  it  has 
however  a  drawback,  as  the  field  appears  thin- 
ner and  more  meager  than  it  is  in  reality. 
*^  Hopetown  oats,"  as  it  is  called,  has  found  its 
way  into  culture  extensively  in  Scotland  and 
has  even  been  introduced  with  success  into  Eng- 
land, Denmark  and  the  United  States.  It  has 
been  one  of  the  best  Scottish  oats  for  more 
than  half  a  century. 

The  next  eight  years  no  single  plant  judged 
worthy  of  selection  on  his  own  farm  attracted 
Shirreff 's  attention.  But  in  the  fall  of  1832  he 
saw  a  beautiful  plant  of  wheat  on  a  neighboring 
farm  and  he  secured  a  head  of  it  with  about  100 
grains.  From  this  he  produced  the  '*  Hope- 
town  wheat."  After  careful  separation  from 
the  kernels  this  original  ear  was  preserved,  and 
was  afterwards  exhibited  at  the  Stirling  Agri- 


Selection  of  Elementary  Species       113 

cultural  Museum.  The  **  Hopetown  wheat  " 
has  proved  to  be  a  constant  variety,  excelling 
the  ordinary  ^'  Hunter's  wheat  "  by  larger 
grains  and  longer  heads;  it  yields  likewise  a 
straw  of  superior  quality  and  has  become  quite 
popular  in  large  districts  of  England  and  Scot- 
land, where  it  is  known  by  the  name  of  ' '  White 
Hunter's  "  from  its  origin  and  the  brilliant 
whiteness  of  its  heads. 

In  the  same  way  Shirreff 's  oats  were  discov- 
ered in  a  single  plant  in  a  field  where  it  was 
isolated  in  order  to  be  brought  into  commerce 
after  multiplication.  It  has  won  the  surname 
of  '^  Make-him-rich. "  Nothing  is  on  record 
about  the  details  of  its  origin. 

Four  valuable  new  varieties  of  wheat  and 
oats  were  obtained  in  this  way  in  less  than  forty 
years.  Then  Shirreff  changed  his  ideas  and  his 
method  of  working.  Striking  specimens  ap- 
peared to  be  too  rare,  and  the  expectation  of  a 
profitable  result  too  small.  Therefore  he  be- 
gan work  on  a  larger  scale.  He  sought  and 
selected  during  the  summer  of  1857  seventy 
heads  of  wheat,  each  from  a  single  plant  show- 
ing some  marked  and  presumably  favorable  pe- 
culiarity. These  were  not  gathered  on  one 
field,  but  were  brought  together  from  all  the 
fields  to  which  he  had  access  in  his  vicinity. 
The  grains  of  each  of  these  selected  heads  were 


114  Elementary  Species 

sown  separately,  and  the  lots  compared  during 
their  whole  life-period  and  chiefly  at  harvest 
time.  Three  of  the  lots  were  judged  of  high 
excellence,  and  they  alone  were  propagated,  and 
proving  to  be  constant  new  varieties  from  the 
outset  were  given  to  the  trade  under  the  names 
of  *^  Shirretf's  bearded  white,"  ''  Shirreff's 
bearded  red,''  and  ^'  Pringle's  wheat.'' 
They  have  found  wdde  acceptance,  and  the  first 
two  of  them  are  still  considered  by  Vilmorin  as 
belonging  to  the  best  wheats  of  France. 

This  second  method  of  Shirreff  evidentlv  is 
quite  analogous  to  the  principle  of  Lagasca  and 
Le  Couteur.  The  previous  assumption  that 
new  varieties  with  striking  features  were  being 
produced  by  nature  from  time  to  time,  was 
abandoned,  and  a  systematic  inquiry  into  the 
worth  of  all  the  divergent  constituents  of  the 
fields  was  begun.  Every  single  ear  at  once 
proved  to  belong  to  a  constant  and  pure  race, 
but  most  of  these  were  only  of  average  value. 
Some  few  however,  excelled  to  a  degTee,  which 
made  them  worth  multiplying,  and  to  be  intro- 
duced into  trade  as  separate  varieties. 

Once  started,  this  new  method  of  comparison, 
selection  and  isolated  multiplication  was  of 
course  capable  of  many  improvements.  The 
culture  in  the  experiment-field  was  improved,  so 
as  to  insure  a  fuller  and  more  rapid  growth. 


Selection  of  Elementary  Species       115 

The  ripe  heads  had  to  be  measured  and  counted 
and  compared  with  respect  to  their  size  and  the 
number  of  their  kernels.  Qualities  of  grain 
and  of  meal  had  to  be  considered,  and  the  in- 
fluence  of  climate  and  soil  could  not  be  over- 
looked. 

Concerning  the  real  origin  of  his  new  types 
Shirreff  seems  never  to  have  been  very  inquisi- 
tive. He  remarks  that  only  the  best  cultivated 
varieties  have  a  chance  to  yield  still  better 
types,  and  that  it  is  useless  to  select  and  sow 
the  best  heads  of  minor  sorts.  He  further  re- 
marks that  it  is  not  probable  that  he 
found  a  new  sport  every  time;  on  the  con- 
trary he  assumes  that  his  selections  had  been 
present  in  the  field  before,  and  during  a  series 
of  succeeding  generations.  How  many  years 
old  they  were,  was  of  course  impossible  to  de- 
termine. But  there  is  no  reason  to  believe  that 
the  conditions  in  the  fields  of  Scotland  were 
different  from  those  observed  on  the  Isle  of 
Jersey  by  Le  Couteur. 

In  the  year  1862  Shirreff  devoted  himself  to 
the  selection  of  oats,  searching  for  the  best 
panicles  from  the  whole  country,  and  compar- 
ing their  offspring  in  his  experimental-garden. 
''  Early  Fellow,''  ''  Fine  Fellow,"  ''  Longfel- 
low "  and  ''  Early  Angus  "  are  very  notable 
varieties   introduced   into   trade   in   this   way. 


116  Elementary  Species 

Some  years  later  Patrick  Sliirreff  described  his 
experiments  and  results  in  a  paper  entitled, 
^^  On  the  improvement  of  cereals,"  but  the  de- 
scriptions are  very  short,  and  give  few  details 
of  systematic  value.  The  leading  principle, 
however,  is  clearly  indicated,  and  anyone  who 
studies  with  care  his  method  of  working,  may 
confidently  attempt  to  improve  the  varieties  of 
his  own  locality  in  the  same  way. 

This  great  principle  of  '*  variety-testing,"  as 
it  has  been  founded  by  Le  Couteur  and  Patrick 
Shirreff,  has  increased  in  importance  ever  since. 
Two  main  features  are  to  be  considered  here. 
One  is  the  production  of  local  races,  the  other 
the  choice  of  the  best  starting-point  for  hybrid- 
izing experiments,  as  is  shown  in  California 
by  the  work  of  Luther  Burbank  in  crossing  dif- 
ferent elementary  species  of  Lilium  pardali- 
num  and  others. 

Every  region  and  locality  has  its  own  condi- 
tions of  climate  and  soil.  Any  ordinary  mixed 
race  will  contain  some  elementary  forms  which 
are  better  adapted  to  a  given  district,  while 
others  are  more  suitable  to  divergent  condi- 
tions. Hence  it  can  readily  be  inferred  that 
the  choice  cannot  be  the  same  for  different  re- 
gions. Every  region  should  select  its  own  type 
from  among  the  various  forms,  and  variety- 
testing  therefore  becomes  a  task  which  every 


Selection  of  Elementary  Species       117 

one  must  undertake  under  his  own  conditions. 
Some  varieties  will  prove,  after  isolation,  to 
be  profitable  for  large  districts  and  perhaps 
for  whole  states.  Others  will  be  found  to  be 
of  more  local  value,  but  in  such  localities  to  excel 
all  others. 

As  an  example  we  may  take  one  of  the  varie- 
ties of  wheat  originated  by  the  Minnesota  Ex- 
periment Station.  Hays  described  it  as  fol- 
lows. It  was  originated  from  a  single  plant. 
From  among  400  plants  of  '^  Blue  stem  "  sev- 
eral of  the  best  were  chosen,  each  growing  sep- 
arately, a  foot  apart  in  every  direction.  Each  of 
the  selected  plants  yielded  500  or  more  grains  of 
wheat,  weighing  10  or  more  grams.  The  seeds 
from  these  selected  plants  were  raised  for  a  few 
years  until  sufficient  was  obtained  to  sow  a 
plot.  Then  for  several  years  the  new  strains 
were  grown  in  a  field  beside  the  parent -variety. 
One  of  them  was  so  much  superior  that  all 
others  were  discarded.  It  was  the  one  named 
''  Minnesota  No.  169."  For  a  large  area  of 
Minnesota  this  wheat  seems  capable  of  yielding 
at  least  1  or  2  bushels  more  grain  per  acre  than 
its  parent  variety,  which  is  the  best  kind  com- 
monly and  almost  universally  found  on  the 
farms  in  southern  and  central  Minnesota. 

It  would  be  quite  superfluous  for  our  present 
purpose  to  give  more  instances.     The  fact  of 


118  Elementary  Species 

the  compound  nature  of  so-called  species  of 
cultivated  plants  seems  to  be  beyond  all  doubt, 
and  its  practical  importance  is  quite  obvious. 

Acclimatization  is  another  process,  which  is 
largely  dependent  on  the  choice  of  adequate 
varieties.  This  is  shown  on  a  large  scale  by 
the  slow  and  gradual  dispersion  of  the  varieties 
of  corn  in  this  country.  The  largest  types  are 
limited  to  temperate  and  subtropical  regions, 
while  the  varieties  capable  of  cultivation  in 
more  northern  latitudes  are  smaller  in  size  and 
stature  and  require  a  smaller  number  of  days 
to  reach  their  full  development  from  seed  to 
seed.  Northern  varieties  are  small  and  short 
lived,  but  the  ''  Forty-day-corn  "  or  "  Quaran- 
tino  maize  '^  is  recorded  to  have  existed  in 
tropical  America  at  the  time  of  Columbus.  In 
preference,  or  rather  to  the  entire  exclu- 
sion of  taller  varieties,  it  has  thriven  on  the 
northern  boundaries  of  the  corn-growing  states 
of  Europe  since  the  very  beginning  of  its  culti- 
vation. 

According  to  Naudin,  the  same  rule  prevails 
with  melons,  cucumbers  and  gherkins,  and  other 
instances  could  easily  be  given. 

Referring  now  to  the  inferences  that  may  be 
drawn  from  the  experience  of  the  breeders  in 
order  to  elucidate  the  natural  processes,  we  will 
return  to  the  whitlow- grasses  and  pansies. 


Selection  of  Elementary  Species      119 

Nature  has  constituted  them  as  groups  of 
slightly  different  constant  forms,  quite  in  the 
same  way  as  wheat  and  oats  and  corn.  Assum- 
ing that  this  happened  ages  ago  somewhere  in 
central  Europe,  it  is  of  course  probable  that 
the  same  differences  in  respect  to  the  influence 
of  climatic  conditions  will  have  prevailed  as 
with  cereals.  Subsequent  to  the  period  which 
has  produced  the  numerous  elementary  spe- 
cies of  the  whitlow-grass  came  a  period  of  wide- 
spread distribution.  The  process  must  have 
been  wholly  comparable  with  that  of  acclimati- 
zation. Some  species  must  have  been  more 
adapted  to  northern  climates,  others  to  the  soils 
of  western  or  eastern  regions  and  so  on.  These 
qualities  must  have  decided  the  general  lines  of 
the  distribution,  and  the  species  must  have 
been  segregated  according  to  their  respective 
climatic  qualities,  and  their  adaptability  to  soil 
and  weather.  A  struggle  for  life  and  a  natural 
selection  must  have  accompanied  and  guided 
the  distribution,  but  there  is  no  reason  to  as- 
sume that  the  various  forms  were  changed 
by  this  process,  and  that  we  see  them  now  en- 
dowed with  other  qualities  than  they  had  at  the 
outset. 

Natural  selection  must  have  played,  in  this 
and  in  a  large  number  of  other  cases,  quite  the 
same  part  as  the  artificial  method  of  variety- 


120  Elementary  Species 

testing.  Indeed  it  may  be  surmised  that  this 
has  been  its  chief  and  prominent  function. 
Taking  up  again  our  metaphor  of  the  sieve  we 
can  assert  that  in  such  cases  climate  and  soil 
exercise  sifting  action  and  in  this  way  the  ap- 
plication of  the  metaphor  becomes  more  defi- 
nite. Of  course,  next  to  the  climate  and  soil  iu 
importance,  come  ecological  conditions,  the  veg- 
etable and  animal  enemies  of  the  plants  and 
other  influences  of  the  same  nature. 

In  conclusion  it  is  to  be  pointed  out  that  this 
side  of  the  problem  of  natural  selection  and  the 
struggle  for  life  appears  to  offer  the  best  pros- 
pects for  experimental,  or  for  continued  statis- 
tical inquiry.  Direct  observations  are  possible 
and  any  comparison  of  numerical  proportions 
of  species  in  succeeding  years  affords  clear 
proof  of  the  part  it  plays.  And  above  all,  such 
observations  can  be  made  quite  independently 
of  doubtful  theoretical  considerations  about 
presumed  changes  of  character. 

The  fact  of  natural  selection  is  plain  and 
it  should  be  studied  in  its  most  simple  condi- 
tions. 


C.  RETROGRADE  VARIETIES 
Lecture  V 

CHARACTERS    OF   RETROGRADE   VARIETIES 

Every  one  admires  the  luxuriance  of  gar- 
den-flowers, and  their  diversity  of  color  and 
form.  All  parts  of  the  world  have  contributed 
to  their  number  and  every  taste  can  find  its 
preference  among  them.  New  forms  produced 
by  the  skill  of  the  breeder  are  introduced  every 
year.  This  has  been  done  mostly  by  crossing 
and  intermingling  the  characters  of  introduced 
species  of  the  same  genus.  In  some  of  the 
cases  the  history  of  our  flowers  is  so  old  that 
their  hybrid  origin  is  forgotten,  as  in  the  case 
of  the  pansies.  Hybridizations  are  still  going 
on  in  other  groups  on  a  large  scale,  and  new 
forms  are  openly  claimed  to  be  of  hybrid  origin. 

Breeders  and  amateurs  generally  have  more 
interest  in  the  results  than  in  the  way  in 
which  they  have  been  brought  about.  Excel- 
lent flowers  and  fruit  recommend  them- 
selves and  there  seems  to  be  no  reason  for  in- 

121 


122  Retrograde  Varieties 

quiring  about  their  origin.  In  some  cases  the 
name  of  the  originator  may  be  so  widely  known 
that  it  adds  weight  to  the  value  of  the  new  form, 
and  therefore  may  advantageously  be  coupled 
with  it.  The  origin  and  history  of  the  greater 
part  of  our  garden-flowers,  fruits  and  vege- 
tables are  obscure;  we  see  them  as  they  are, 
and  do  not  know  from  whence  they  came.  The 
original  habitat  for  a  whole  genus  or  for  a 
species  at  large,  may  be  known,  but  questions  as 
to  the  origin  of  the  single  forms,  of  which  it  is 
built  up,  ordinarily  remain  unanswered. 

For  these  reasons  we  are  restricted  in  most 
cases  to  the  comparison  of  the  forms  before  us. 
This  comparison  has  led  to  the  general  use 
of  the  term  ''  variety  "  in  opposition  to 
*^  species."  The  larger  groups  of  forms, 
which  are  known  to  have  been  introduced  as 
such  are  called  species.  All  forms  which  by 
their  characters  belong  to  such  a  species  are 
designated  as  varieties,  irrespective  of  their 
svstematic  relation  to  the  form,  considered  as 
the  ancestor  of  the  group. 

Hence,  we  distinguish  between  '^  hybrid  va- 
rieties "  and  ^^  pure  varieties  "  according  to 
their  origin  from  different  parents  or  from  a 
single  line  of  ancestors.  Moreover,  in  both 
groups  the  forms  may  be  propagated  by  seeds, 
or  in  the  vegetative  way  by  buds,  by  grafting  or 


Retrograde  Varieties  123 

by  cutting,  and  this  leads  to  the  distinction  of 
^ '  seed-varieties  ' '  and  ' '  vegetative  varieties. ' ' 
In  the  first  case  the  inheritance  of  the  special 
characters  through  the  seeds  decides  the  status 
of  the  variety,  in  the  latter  case  this  point  is  left 
wholly  out  of  consideration. 

Leaving  aside  all  these  different  types,  we 
are  concerned  here  only  with  the  "  seed-varie- 
ties ' '  of  pure  origin,  or  at  least  with  those,  that 
are  supposed  to  be  so.  Hybridization  and 
vegetative  multiplication  of  the  hybrids  no 
doubt  occur  in  nature,  but  they  are  very  rare, 
when  compared  with  the  ordinary  method  of 
propagation  by  seed.  *^  Seed-varieties  ''  may 
further  be  divided  into  constant  and  inconstant 
ones.  The  difference  is  very  essential,  but  the 
test  is  not  always  easy  to  apply.  Constant 
varieties  are  as  sharply  defined  and  as  narrowly 
limited  as  are  the  best  wild  species,  while  in- 
constant types  are  cultivated  chiefly  on  account 
of  their  wide  range  of  form  and  color.  This 
diversity  is  repeated  yearly,  even  from  the 
purest  seed.  We  will  now  discuss  the  constant 
seed- varieties,  leaving  the  inconstant  and  ever- 
sporting  types  to  a  subsequent  lecture. 

In  this  way  we  may  make  an  exact  inquiry 
into  the  departures  from  the  species  which  are 
ordinarily  considered  to  constitute  the  essential 
character  of  such  a  constant  and  pure  seed- 


124  Retrograde  Varieties 

variety  and  need  only  compare  these  differ- 
ences with  those  that  distinguish  the  elementary 
species  of  one  and  the  same  group  from  each 
other. 

Two  points  are  very  striking.  By  far  the 
greatest  part  of  the  ordinary  garden-varieties 
differ  from  their  species  by  a  single  sharp  char- 
acter only.  In  derivative  cases  two,  three  or 
even  more  such  characters  may  be  combined  in 
one  variety,  for  instance,  a  dwarfed  variety  of 
the  larkspur  may  at  the  same  time  bear  white 
flowers,  or  even  double  white  flowers,  but  the 
individuality  of  the  single  characters  is  not  in 
the  least  obscured  by  such  combinations. 

The  second  point  is  the  almost  general  oc- 
currence of  the  same  variety  in  extended  series 
of  species.  White  and  double  flowers,  varie- 
gated leaves,  dwarfs  and  many  other  instances 
may  be  cited.  It  is  precisely  this  universal 
repetition  of  the  same  character  that  strikes  us 
as  the  essential  feature  of  a  variety. 

And  again  these  two  characteristics  may  now 
be  considered  separately.  Let  us  begin  with 
the  sharpness  of  the  varietal  characters.  In 
this  respect  varieties  differ  most  obviously 
from  elementary  species.  These  are  distin- 
guished from  their  nearest  allies  in  almost  all 
organs.  There  is  no  prominent  distinctive 
feature   between   the    single   forms   of   Br  aba 


Retrograde  Varieties  125 

verna,  H elianthemum  or  of  Taraxacum;  all 
characters  are  almost  equally  concerned.  The 
elementary  species  of  Draba  are  characterized, 
as  we  have  seen,  by  the  forms  and  the  hairiness 
of  the  leaves,  the  number  and  height  of  the 
flower-stalks,  the  breadth  and  incision  of  the 
petals,  the  forms  of  the  fruits,  and  so  on. 
Every  one  of  the  two  hundred  forms  included 
in  this  collective  species  has  its  own  type,  which 
it  is  impossible  to  express  by  a  single  term. 
Their  names  are  chosen  arbitrarily.  Quite  the 
contrary  is  the  case  with  most  of  the  varieties, 
for  which  one  word  ordinarily  suffices  to  ex- 
press the  whole  ditference. 

White  varieties  of  species  with  red  or  blue 
flowers  are  the  most  common  instances.  If  the 
species  has  a  compound  color  and  if  only  one 
of  the  constituents  is  lost,  partially  colored 
types  arise  as  inAgrostemmaCoronariabicolor, 
Or  the  spots  may  disappear  and  the  color  be- 
come uniform  as  in  Gentiana  punctata  concolor 
and  the  spotless  Arum  or  Arum  maculatum  im- 
maculatum.  Absence  of  hairs  produces  forms 
as  Biscutella  Icevigata  glabra;  lack  of  prickles 
gives  the  varieties  known  as  inermis,  as  for  in- 
stance. Ranunculus  arvensis  inermis,  Cytisus 
prostratus  has  a  variety  clliata,  and  Solanuni 
Dulcamara,  or  the  bitter-sweet,  has  a  va- 
riety  called   tomentosum.     The   curious  mon- 


126  Retrograde  Varieties 

opliyllons  variety  of  the  strawberry  and  many 
other  forms  will  be  discussed  later. 

To  enlarge  this  list  it  would  only  be  necessary 
to  extract  from  a  flora,  or  from  a  catalogue  of 
horticultural  plants,  the  names  of  the  varieties 
enumerated  therein.  In  nearly  every  instance, 
where  true  varieties  and  not  elementary  species 
are  concerned,  a  single  term  expresses  the 
whole  character. 

Such  a  list  would  also  serve  to  illustrate  the 
second  point  since  the  same  names  would  recur 
frequently.  Long  lists  of  varieties  are  called 
alha,  or  inermis,  or  canescens  or  lutea,  and 
many  genera  contain  the  same  appellations.  In 
some  instances  the  systematists  use  a  diversity 
of  names  to  convey  exactly  the  same  idea,  as  if 
to  conceal  the  monotony  of  the  character,  as 
for  instance  in  the  case  of  the  lack  of  hairs, 
which  is  expressed  by  the  varietal  names  of 
Papaver  duhium  glahrum,  Arahis  ciliata  gla- 
hrata,  Arabis  hirsuta  glaherrima,  Veronica 
spicata  nitens,  Amygdalus  persica  laevis, 
Paeonia  corallina  leiocarpa,  &c. 

On  the  contrary  we  find  elementarj^  species  in 
different  genera  based  on  the  greatest  possible 
diversity  of  features.  The  forms  of  Taraxacum 
or  Helianthemum  do  not  repeat  those  of  Draba 
or  Viola.  In  roses  and  brambles  the  distinguish- 
ing features  are  characteristic  of  the  type,  as 


Retrograde  Varieties  127 

they  are  evidently  derived  from  it  and  limited 
to  it.  And  this  is  so  true  that  nobody  claims 
the  grade  of  elementary  species  for  white  roses 
or  white  brambles,  but  everyone  recognizes  that 
forms  diverging  from  the  nearest  species  by 
a  single  character  only,  are  to  be  regarded  as 
varieties. 

This  general  conviction  is  the  basis  on  which 
we  may  build  up  a  more  sharply  defined  distinc- 
tion between  elementary  species  and  varieties. 
It  is  an  old  rule  in  systematic  botany,  that  no 
form  is  to  be  constituted  a  species  upon  the 
basis  of  a  single  character.  All  authors  agree 
on  this  point;  specific  differences  are  derived 
from  the  totality  of  the  attributes,  not  from  one 
organ  or  one  quality.  This  rule  is  intimately 
connected  with  the  idea  that  varieties  are  de- 
rived from  species.  The  species  is  the  typical, 
really  existing  form  from  which  the  variety  has 
originated  by  a  definite  change.  In  enumer- 
ating the  different  forms  the  species  is  distin- 
guished by  the  term  of  genuine  or  typical,  often 
only  indicated  as  a  or  the  first;  then  fol- 
low the  varieties  sometimes  in  order  of  their 
degree  of  difference,  sometimes  simply  in  alpha- 
betical order.  In  the  case  of  elementary  species 
there  is  no  real  type;  no  one  of  them  predom- 
inates because  all  are  considered  to  be  equal  in 
rank,  and  the  systematic  species  to  which  they 


128  Retrograde  Varieties 

are  referred  is  not  a  really  existing  form,  but  is 
the  abstraction  of  the  common  type  of  all,  just 
as  it  is  in  the  case  of  a  genus  or  of  a  family. 

Summarizing  the  main  points  of  this  discus- 
sion, we  find  that  elementary  species  are  of 
equal  rank  and  together  build  up  the  collective 
or  systematic  ideal  species.  Varieties  on  the 
other  hand  are  derived  from  a  real  and  com- 
monlj",  still  existing  type. 

I  hope  that  I  have  succeeded  in  showing  that 
the  difference  between  elementary  species,  or,  as 
they  are  often  called,  smaller  or  subspecies,  on 
the  one  hand  and  varieties  on  the  other,  is  quite 
a  marked  one.  However,  in  order  to  recognize 
this  principle  it  is  necessary  to  limit  the  term 
variety,  to  those  propagating  themselves  by 
seed  and  are  of  pure  and  not  of  hybrid  origin. 

But  the  principle  as  stated  here,  does  not  in- 
volve an  absolute  contrast  between  two  groups 
of  characters.  It  is  more  a  difference  in  our 
knowledge  and  appreciation  of  them  than  a  dif- 
ference in  the  things  themselves.  The  characters 
of  elementary  species  are,  as  a  rule,  new  to  us, 
while  those  of  varieties  are  old  and  familiar. 
It  seems  to  me  that  this  is  the  essential  point. 

And  what  is  it  that  makes  us  familiar  with 
them?  Obviously  the  continuous  recurrence  of 
the  same  changes,  because  by  a  constant  repeti- 
tion they  must  of  course  lose  their  novelty. 


Retrograde  Varieties  129 

Presently  we  shall  look  into  these  characters 
more  in  detail  and  then  we  shall  find  that  they 
are  not  so  simple  as  might  be  supposed  at  first 
sight;  but  precisely  because  we  are  so  familiar 
with  them,  we  readily  see  that  their  different 
features  really  belong  to  a  single  character; 
while  in  elementary  species  everything  is  so 
new  that  it  is  impossible  for  us  to  discern  the 
unities  of  the  new  attributes. 

If  we  bear  in  mind  all  these  difficulties  we 
cannot  wonder  at  the  confusion  on  this  ques- 
tion that  seems  to  prevail  everywhere.  Some 
authors  following  Linnaeus  simply  call  all  the 
subdivisions  of  species,  varieties;  others  fol- 
low Jordan  and  avoid  the  difficulty  by  desig- 
nating all  smaller  forms  directly  as  species. 
The  ablest  systematists  prefer  to  consider  the 
ordinary  species  as  collective  groups,  calling 
their  constituents  "  The  elements  of  the  spe- 
cies," as  was  done  by  A.  P.  De  Candolle,  Alph. 
De  Candolle  and  Lindley. 

By  this  method  they  clearly  point  out  the  dif- 
ference between  the  subdivisions  of  wild  spe- 
cies as  they  ordinarily  occur,  and  the  varieties 
in  our  gardens,  which  would  be  very  rare,  were 
they  not  singled  out  and  preserved. 

Our  familiarity  with  a  character  and  our 
grounds  for  calling  it  an  old  acquaintance  may 
result  from  two  causes,  which  in  judging  a  new 


130  Retrograde  Varieties 

variety  are  essentially  different.  The  charac- 
ter in  question  may  be  present  in  the  given  spe- 
cies or  it  may  be  lacking,  but  present  in  the  other 
group.  In  the  first  case  a  variety  can  only  be 
formed  by  the  loss  of  the  character,  in  the  sec- 
ond case  it  arises  by  the  addition  of  a  new  one. 

The  first  mode  may  be  called  a  negative  pro- 
cess, while  the  second  is  then  to  be  designated 
as  positive.  And  as  it  is  more  easy  to  lose  what 
one  has  than  to  obtain  something  new,  negative 
varieties  are  much  more  common  than  are  posi- 
tive ones. 

Let  us  now  take  an  instance  of  a  character 
that  is  apt  to  vary  in  both  ways,  for  this  is  ob- 
viously the  best  way  of  making  clear  what  is 
meant  by  a  negative  and  a  positive  change. 

In  the  family  of  the  composites  we  find  a 
group  of  genera  with  two  forms  of  florets  on 
each  flower-head.  The  hermaphrodite  ones  are 
tubular  with  5,  or  rarely  4,  equal  teeth,  and  oc- 
cupy the  center  of  the  head.  These  are  often 
called  the  flosculous  florets  or  disk-florets. 
Those  of  the  circumference  are  ligulate  and 
ordinarily  unisexual,  without  stamens.  In  many 
cases  they  are  sterile,  having  only  an  imperfect 
ovary.  They  are  large  and  brightly  colored  and 
are  generally  designated  as  ray-florets.  As  in- 
stances we  may  cite  the  camomile  (AntJiemis 
nohilis),  the  wild  camomile  {Matricaria  Cham- 


Retrograde  Varieties  131 

omilla),  the  yarrow  {Achillea  Millefolium), 
the  daisies,  the  Dahlia  and  many  others. 
Species  occur  in  this  group  of  plants  from  time 
to  time  that  lack  the  ray-florets,  as  in  the  tansy 
(Tanacetum  vulgar e)  and  some  artemisias. 
And  the  genus  of  the  marigolds  or  Bidens  is 
noted  for  containing  both  of  these  types.  The 
smaller  and  the  three-toothed  marigold  (B. 
cernua  and  B.  tripartita)  are  very  common 
plants  of  wet  soil  and  swamps,  ordinarily  lack- 
ing the  ray-florets,  and  in  some  countries  they 
are  very  abundant  and  wholly  constant  in  this 
respect,  never  forming  radiate  flower-heads. 
On  the  other  hand  the  white-flowered  and  the 
purple  marigold  (B.  leucantha  and  B.  atropur- 
purea)  are  cultivated  species  of  our  gardens, 
prized  for  their  showy  flower-heads  with  large 
white  or  deeply  colored,  nearly  black-purple 
florets. 

Here  we  have  opportunity  to  observe  positive 
and  negative  varieties  of  the  same  character. 
The  smaller,  and  the  three-toothed  marigold 
occur  from  time  to  time,  provided  with  ray- 
florets,  showing  a  positive  variation.  And  the 
white  marigold  has  produced  in  our  gardens  a 
variety  without  rays.  Such  varieties  are  quite 
constant,  never  returning  to  the  old  species. 

Positive  and  negative  varieties  of  this  kind 
are  by  no  means  rare  among  the  compositae. 


132  Retrograde  Varieties 

In  systematic  works  the  positive  ones  are  as  a 
rule  called  '*  radiate,"  and  the  negative  ones 
**  discoid."  Discoid  forms  of  the  ordinarj^ 
camomile,  of  the  daisy,  of  some  asters  {Aster 
Tripolmm),  and  of  some  centauries  have  been 
described.  Radiate  forms  have  been  observed 
in  the  tansy  {Tanacetum  vulgar e),  the  common 
horse-weed  or  Canada  fleabane  {Erigeron  cana- 
densis) and  the  common  groundsel  (Senecio 
vidgaris).  Taken  broadly  the  negative  varie- 
ties seem  to  be  somewhat  more  numerous  than 
the  positive  ones,  but  it  is  very  difficult  to  come 
to  a  definite  conclusion  on  this  point.  . 

Quite  the  contrary  is  the  case  with  regard  to 
the  color-varieties  of  red  and  blue  flowers. 
Here  the  loss  of  color  is  so  common  that  every 
one  could  give  long  lists  of  examples  of  it.  Lin- 
naeus himself  supposed  that  no  blue  or  red-col- 
ored wild  species  would  be  without  a  white  va- 
riety. It  is  well  known  that  he  founded  his 
often  criticized  prescript  never  to  trust  to  color 
in  recognizing  or  describing  a  species,  on  this 
belief. 

On  the  other  hand  there  are  some  red  varie- 
ties of  white-flowered  species.  But  they  are 
very  rare,  and  little  is  known  about  their  charac- 
ters or  constancy.  Blue  varieties  of  white  spe- 
cies are  not  found.  The  yarrow  (Achillea  Mil- 
lefolium) has  a  red-flowered  form,  which  occurs 


Retrograde  Varieties  133 

from  time  to  time  in  sunny  and  sandy  localities. 
I  have  isolated  it  and  cultivated  it  during  a 
series  of  years  and  during  many  generations. 
It  is  quite  true  to  its  character,  but  the  degree 
of  its  coloring  fluctuates  between  pink  and  white 
and  is  extremely  variable.  Perhaps  it  can  be 
considered  as  an  inconstant  variety.  A  red- 
flowered  form  of  the  common  Begonia  semper- 
florens  is  cultivated  under  the  name  of  ^'  Ver- 
non," the  white  hawthorn  (Crataegus  Oxya- 
cantha)  is  often  seen  with  red  flowers,  and  a 
pink-flowered  variety  of  the  '^  Silverchain  "  or 
''  Bastard  acacia  "  (Robinia  Pseud-Acacia)  is 
not  rarely  cultivated.  The  '*  Crown  "  variety 
of  the  yellow  wall-flower  and  the  black  varieties, 
are  also  to  be  considered  as  positive  color- 
variations,  the  black  being  due  in  the  latter 
cases  to  a  very  great  amount  of  the  red  pigment. 
Among  fruits  there  are  also  some  positive 
red  varieties  of  greenish  or  yellowish  species,  as 
for  instance  the  red  gooseberry  (Ribes  Grossu- 
laria)  and  the  red  oranges.  The  red  hue  is  far 
more  common  in  leaves,  as  seen  among  herbs,  in 
cultivated  varieties  of  Coleus  and  in  the  brown- 
leaved  form  of  the  ordinary  white  clover,  among 
trees  and  shrubs  in  the  hazelnut  (Corylus),  the 
beach  '(Fagus),  the  birch  (Bettda),  the  barberry 
(Berberis)  and  many  others.  But  though  most 
of  these  forms  are  very  ornamental  and  abun- 


134  Retrograde  Varieties 

dant  in  parks  and  gardens,  little  is  as  yet  known 
concerning  the  origin  of  their  varietal  attributes 
and  their  constancy,  when  propagated  by  seeds. 
Besides  the  ray-florets  and  the  colors,  there  are 
of  course  a  great  many  other  characters  in 
which  varieties  may  differ  from  their  species. 
In  most  of  the  cases  it  is  easy  to  discern 
whether  the  new  character  is  a  positive  or  a 
negative  one.  And  it  is  not  at  all  necessary  to 
scrutinize  very  narrowly  the  list  of  forms  to  be- 
come convinced  that  the  negative  form  is  the 
one  which  prevails  nearly  everywhere,  and  that 
positive  aberrations  are  in  a  general  sense  so 
rare  that  they  might  even  be  taken  for  exce]3- 
tions  to  the  rule. 

Many  organs  and  many  qualities  may  be  lost 
in  the  origination  of  a  variety.  In  some  in- 
stances the  petals  may  disappear,  as  in  Nigella, 
or  the  stamens,  as  in  the  Guelder-rose  {Vibur- 
num Opulus)  and  the  Hortensia  and  in  some 
bulbs  even  the  whole  flowers  may  be  wanting, 
as  in  the  beautiful  "  Plumosa  "  form  of  the 
cultivated  grape-hyacinth  or  Muscari  comosum. 
Fruits  of  the  pineapples  and  bananas  without 
seeds  are  on  record  as  well  as  some  varieties  of 
apples  and  pears,  of  raisins  and  oranges.  And 
some  years  ago  Mr.  Riviere  of  Algeria  de- 
scribed a  date  growing  in  his  garden  that  forms 
fruit  without  pits.     The  stoneless  plum  of  Mr. 


Retrograde  Varieties  135 

Burbank  of  Santa  Rosa,  California,  is  also  a 
very  curious  variety,  the  kernel  of  which  is  fully 
developed  but  naked,  no  hard  substance  inter- 
vening between  it  and  the  pulp. 

More  curious  still  are  the  unbranched  varie- 
ties consisting  of  a  single  stem,  as  may  be  seen 
sometimes  in  the  corn  or  maize  and  in  the  fir. 
Fir-trees  of  some  three  or  four  meters  in  height 
without  a  single  branch,  wholly  naked  and  bear- 
ing leaves  only  on  the  shoots  of  the  last  year's 
growth  at  the  apex  of  the  tree,  may  be  seen.  Of 
course  they  cannot  bear  seed,  and  so  it  is  with 
the  sterile  maize,  which  never  produces  any 
seed-spikes  or  staminate  flowers.  Other  seed- 
less varieties  can  be  propagated  by  buds ;  their 
origin  is  in  most  cases  unknown,  and  we  are  not 
sure  as  to  whether  they  should  be  classified  with 
the  constant  or  with  the  inconstant  varieties. 

A  very  curious  loss  is  that  of  starch  in  the 
grains  of  the  sugar-corn  and  the  sugar-peas. 
It  is  replaced  by  sugar  or  some  allied  substance 
(dextrine).  Equally  remarkable  is  the  loss  of 
the  runners  in  the  so-called  '^  Gaillon  "  straw- 
berries. 

Among  trees  the  pendulous  or  weeping,  and 
the  broomlike  or  fastigiate  forms  are  very 
marked  varieties,  which  occur  in  species  belong- 
ing to  quite  different  orders.  The  ash,  the 
beach,  some  willows,  many  other  trees  and  some 


136  Retrograde  Varieties 

finer  species  of  garden-plants,  as  Sophora  jap- 
onica,  have  given  rise  to  weeping  varieties,  and 
the  yew-tree  or  Taxus  has  a  fastigiate  form 
which  is  much  valued  because  of  its  ascending 
branches  and  pyramidal  habit.  So  it  is  with 
the  pyramidal  varieties  of  oaks,  elms,  the  bas- 
tard-acacia and  some  others. 

It  is  generally  acknowledged  that  these  forms 
are  to  be  considered  as  varieties  on  the  ground 
of  their  occurrence  in  so  wide  a  range  of  species, 
and  because  they  always  bear  the  same  attrib- 
utes. The  pendulous  forms  owe  their  peculiar- 
ity to  a  lengthening  of  the  branches  and  a  loss 
of  their  habit  of  growing  upwards ;  they  are  too 
weak  to  retain  a  vertical  j)osition  and  the  re- 
sponse to  gravity,  which  is  ordinarily  the  cause 
of  the  upright  growth,  is  lacking  in  them.  As 
far  as  we  know,  the  cause  of  this  weeping  habit 
is  the  same  in  all  instances.  The  fastigiate 
trees  and  shrubs  are  a  counterpart  of  the  weep- 
ing forms.  Here  the  tendency  to  grow  in  a 
horizontal  direction  is  lacking,  and  with  it  the 
bilateral  and  symmetric  structure  of  the 
branches  has  disappeared.  In  the  ordinary 
yew-tree  the  upright  stem  bears  its  needles 
equally  distributed  around  its  circumference, 
but  on  the  branches  the  needles  are  inserted  in 
two  rows,  one  to  the  left  and  one  to  the  right. 
All  the  needles  turn  their  upper  surfaces  up- 


Retrograde  Varieties  137 

wards,  and  their  lower  surfaces  downwards,  and 
all  of  them  are  by  this  means  placed  in  a  single 
horizontal  plane,  and  branching  takes  place  in 
the  same  plane.  Evidently  this  general  ar- 
rangement is  another  response  to  gravity,  and 
it  is  the  failure  of  this  reaction  which  induces 
the  branches  to  grow  upwards  and  to  behave 
like  stems. 

Both  weeping  and  fastigiate  characters  are 
therefore  to  be  regarded  as  steps  in  a  negative 
direction,  and  it  is  highly  important  that  even 
such  marked  departures  occur  without  transi- 
tions or  intermediate  forms.  If  these  should 
occur,  though  ever  so  rarely,  they  would  proba- 
bly have  been  brought  to  notice,  on  account  of 
the  great  prospect  the  numerous  instances 
would  offer.  The  fact  that  they  are  lacking, 
proves  that  the  steps,  though  apparently  great, 
are  in  reality  to  be  considered  as  covering  single 
units,  that  cannot  be  divided  into  smaller  parts. 
Unfortunately  we  are  still  in  the  dark  as  to  the 
question  of  the  inheritance  of  these  forms, 
since  in  most  cases  it  is  difficult  to  obtain  pure 
seed. 

We  now  consider  the  cases  of  the  loss  of  su- 
perficial organs,  of  which  the  nectarines  are 
example.  These  are  smooth  peaches,  lacking 
the  soft  hairy  down,  that  is  a  marked  pecul- 
iarity of  the  true  peaches.     They  occur  in  differ- 


138  Retrograde  Varieties 

ent  races  of  the  peach.  As  early  as  the  begin- 
ning of  the  past  century,  Gallesio  described  no 
less  than  eight  subvarieties  of  nectarines,  each 
related  to  a  definite  race  of  peach.  Most  of 
them  reproduce  themselves  truly  from  seed,  as 
is  well  known  in  this  country  concerning  the 
clingstones,  freestones  and  some  other  types. 
Nectarines  have  often  varied,  giving  rise  to  new 
sorts,  as  in  the  case  of  the  white  nectarine  and 
many  others  differing  greatly  in  appearance 
and  flavor.  On  the  other  hand  it  is  to  be  re- 
marked, that  the  trees  do  not  differ  in  other  re- 
spects and  cannot  be  distinguished  while  young, 
the  varietal  mark  being  limited  to  the  loss  of 
the  down  on  the  fruit.  Peaches  have  been 
known  to  produce  nectarines,  and  nectarines  to 
yield  true  peaches.  Here  we  have  another  in- 
stance of  positive  and  negative  steps  with  refer- 
ence to  the  same  character,  but  I  cannot  with- 
hold an  expression  of  some  doubt  as  to  the  possi- 
bility of  crossing  and  subsequently  splitting  up 
of  the  hybrids  as  a  more  probable  explanation 
of  at  least  some  of  the  cases  quoted  by  various 
writers. 

Smooth  or  glabrous  varieties  often  occur,  and 
some  of  them  have  already  been  cited  as  in- 
stances of  the  multiplication  of  varietal  names. 
Positive  aberrations  are  rather  rare,  and  are 
mostly  restricted  to  a  greater  density  of  the 


Retrograde  Varieties  139 

pubescence  in  some  hairy  species,  as  in  Galeop- 
sis  Ladanum  canescens,  Lotus  corniculatus 
hirsutus  and  so  on.  But  Veronica  scutellata  is 
smooth  and  has  a  pubescent  variety,  and  Cyti- 
sus  prostratus  and  C.  spinescens  are  each  re- 
corded to  have  a  ciliate  form. 

Comparable  with  the  occurrence  and  the  lack 
of  hairs,  is  the  existence  or  deficiency  of  the 
glaucous  effect  in  leaves,  as  is  well  known  in  the 
common  Ricinus.  Here  the  glaucous  appear- 
ance is  due  to  wax  distributed  in  fine  particles 
over  the  surface  of  the  leaves,  and  in  the  green 
variety  this  wax  is  lacking.  Other  instances 
could  be  given  as  in  the  green  varieties  of  Pap- 
aver  alpimim  and  Rumex  scutatus.  No  positive 
instances  are  recorded  in  this  case. 

Spines  and  prickles  may  often  disappear  and 
give  rise  to  unarmed  and  defenceless  types. 
Of  the  thorn-apples  both  species,  the  white- 
flowered  Datura  Stramonium  and  the  purple 
D.  Tatida  have  such  varieties.  Spinach  has 
a  variety  called  the  "  Dutch,"  which  lacks 
the  prickles  of  the  fruit;  it  is  a  very  old 
form  and  absolutely  constant,  as  are  also 
the  thornless  thorn-apples.  Last  year  a  very 
curious  instance  of  a  partial  loss  of  prickles  was 
discovered  by  Mr.  Cockerell  of  East  Las  Vegas 
in  New  Mexico.  It  is  a  varietv  of  the  American 
cocklebur,    often    called    sea-burdock,    or    the 


140  Retrograde  Varieties 

hedgehog-burweed,  a  stout  and  common  weed 
of  the  western  States.  Its  latin  name  is  Xan- 
thium  canadense  or  X.  commune  and  the  form 
referred  to  is  named  by  Mr.  Cockerell  X.  Woo- 
toni,  in  honor  of  Professor  E.  0.  Wooton  who 
described  the  first  collected  specimens. 

The  burs  of  the  common  species  are  densely 
covered  with  long  prickles,  which  are  slightly 
hooked  at  the  apex.  In  the  new  form,  which  is 
similar  in  all  other  respects  to  the  common 
cocklebur,  the  burs  are  more  slender  and  the 
prickles  much  less  numerous,  about  25  to  the 
bur  and  mostly  stouter  at  the  base.  It  occurs 
abundantly  in  New  Mexico,  always  growing 
with  the  common  species,  and  seems  to  be  quite 
constant  from  seed.  Mr.  Cockerell  kindly  sent 
me  some  burs  of  both  forms,  and  from  these  I 
raised  in  my  garden  last  year  a  nice  lot  of  the 
common,  as  well  as  of  the  Wootoni  plants. 

Spineless  varieties  are  recorded  for  the  bas- 
tard-acacia, the  holly  and  the  garden  goose- 
berry (Ribes  Grossularia,  or  R.  Uva-crispa).  A 
spineless  sport  of  the  prickly  Broom  {Ulex  eu- 
ropceiis)  has  been  seen  from  time  to  time,  but  it 
has  not  been  propagated. 

Summarizing  the  foregoing  facts,  we  have  ex- 
cellent evidence  of  varieties  being  produced 
either  by  the  loss  of  some  marked  peculiarity  or 
by  the  acquisition  of  others  that  are  already 


Retrograde  Varieties  141 

present  in  allied  species.  There  are  a  great 
many  cases  however,  in  which  the  morpho- 
logic cause  of  the  dissimilarity  is  not  so  easily 
discerned.  But  there  is  no  reason  to  doubt  that 
most  of  them  will  be  found  to  conform  to  the 
rule  on  closer  investigation.  Therefore  we  can 
consider  the  following  as  the  principal  ditfer- 
ence  between  elementary  species  and  varieties; 
that  the  first  arise  by  the  acquisition  of  entirely 
new  characters,  and  the  latter  by  the  loss  of 
existing  qualities  or  by  the  gain  of  such  pecul- 
iarities as  may  already  be  seen  in  other  allied 
species. 

If  we  suppose  elementary  species  and  varie- 
ties originated  by  sudden  leaps  or  mutations, 
then  the  elementary  species  have  mutated  in  the 
line  of  progression,  some  varieties  have 
mutated  in  the  line  of  retrogression,  while  others 
have  diverged  from  their  parental  types  in  a 
line  of  degression,  or  in  the  way  of  repetition. 
This  conception  agrees  quite  well  with  the  cur- 
rent idea  that  in  the  building  up  of  the  vegeta- 
ble kingdom  according  to  the  theory  of  descent, 
it  is  species  that  form  the  links  of  the  chain 
from  the  lower  forms  to  the  more  highly  organ- 
ized later  derivatives.  Otherwise  expressed, 
the  system  is  built  up  of  species,  and  varieties 
are  only  local  and  lateral,  but  never  of  real 
importance  for  the  whole  structure. 


142  Retrograde  Varieties 

Heretofore  we  have  generally  assumed,  that 
varieties  differ  from  the  parent-species  in  a  sin- 
gle character  only,  or  at  least  that  only  one  need 
be  considered.  We  now  come  to  the  study  of 
those  varieties,  which  differ  in  more  than  one 
character.  Of  these  there  are  two  types.  In 
the  first  the  points  of  dissimilarity  are  inti- 
mately connected  with  one  another,  in  the 
second  they  are  more  or  less  independent. 

The  mutually  related  peculiarities  may  be 
termed  correlative,  and  we  therefore  speak,  in 
such  cases,  of  correlative  variability.  This 
phenomenon  is  of  the  highest  importance  and 
is  of  general  occurrence.  But  before  describing 
some  examples,  it  is  as  well  to  note  that  in  the 
lecture  on  fluctuating  variability,  cases  of  a 
totally  different  nature  will  be  dealt  with,  which 
unfortunately  are  designated  by  the  same 
term.  Such  merely  fluctuating  variations  are 
therefore  to  be  left  out  of  the  present  dis- 
cussion. 

The  purple  thorn-apple,  which  is  considered 
by  some  writers  as  a  variety  of  the  white-flow- 
ered species  or  Datura  Stramonium,  and  by 
others  as  a  separate  species,  D.  Tatula,  will 
serve  as  an  illustration.  But  as  its  distinguish- 
ing attributes,  as  far  as  we  are  concerned  with 
them  here,  are  of  the  nature  described  above  as 
characteristic  of  varietal  peculiarities  no  ob- 


f 


Retrograde  Varieties  143 

jection  can  be  made  to  our  using  them  as  a  case 
of  correlative  variability. 

The  essential  character  of  the  purple  thorn- 
apple  lies  in  the  color  of  the  flowers,  which  are 
of  a  very  beautiful  pale  blue.  But  this  color 
is  not  limited  to  the  corolla.  It  is  also  to  be 
seen  in  the  stems  and  in  the  stalks  and  veins  of 
the  leaves,  which  are  stained  with  a  deep  purple, 
the  blue  color  being  added  to  the  original  green. 
Even  on  the  surface  of  the  leaves  it  may  spread 
into  a  purplish  hue.  On  the  stems  it  is  to  be 
met  with  everywhere,  and  even  the  young  seed- 
lings show  it.  This  is  of  some  importance,  as 
the  young  plants  when  unfolding  their  cotyle- 
dons and  primary  leaves,  may  be  distinguished 
by  this  means  from  the  seedlings  of  the  white- 
flowered  species.  In  crossing  experiments  it  is 
therefore  possible  to  distinguish  the  whites  and 
the  blues,  even  in  young  seedlings,  and  ex- 
perience shows  that  the  correlation  is  quite 
constant.  The  color  can  always  be  relied  upon ; 
if  lacking  in  the  seedlings,  it  will  be  lacking  in 
the  stems  and  flowers  also;  but  if  the  axis  of 
the  young  plant  is  ever  so  slightly  tinged,  the 
color  will  show  itself  in  its  beautv  in  the  later 
stages  of  the  life  of  the  plant. 

This  is  what  we  term  correlation.  The  colors 
of  the  different  organs  are  always  in  agreement. 
It  is  true  that  they  require  the  concurrence  of 


144  Retrograde  Varieties 

light  for  development,  and  that  in  the  dark  or  in 
a  faint  light  the  seedlings  are  apt  to  remain 
green  when  they  should  become  purple,  but 
aside  from  such  consideration  all  organs  always 
come  true  to  their  color,  whether  pure  green  and 
white,  or  whether  these  are  combined  with  the 
blue  tinge.  This  constancy  is  so  absolute  that 
the  colors  of  the  different  organs  convey  the 
suggestion,  that  they  are  only  separate  marks 
of  a  single  character. 

It  is  on  this  suggestion  that  we  must  work,  as 
it  indicates  the  cause  of  the  correlation.  Once 
present,  the  faculty  of  producing  the  anthocyan, 
the  color  in  question,  will  come  into  activity 
wherever  and  whenever  opportunity  presents 
itself.  It  is  the  cell-sap  of  the  ordinary  cell- 
tissue  or  parenchyma,  which  is  colored  by  the 
anthocyan,  and  for  this  reason  all  organs  pos- 
sessing this  tissue,  may  exhibit  the  color  in  ques- 
tion. 

Thus  the  color  is  not  a  character  belonging  to 
any  single  organ  or  cell,  nor  is  it  bound  to  a 
morphologic  unit ;  it  is  a  free,  physiologic  qual- 
ity. It  is  not  localized,  but  belongs  to  the  en- 
tire plant.  If  we  wish  to  assume  for  its  basis 
material  representative  particles,  these  parti- 
cles must  be  supposed  to  be  diffused  throughout 
the  whole  body  of  the  plant. 

This  conception  of  a  physiologic  unit  as  the 


Retrograde  Varieties  145 

cause  of  colors  and  other  qualities  is  evidently 
opposed  to  the  current  idea  of  the  cells  and  tis- 
sues as  the  morphologic  units  of  the  plants. 
But  I  do  not  doubt,  that  in  the  long  run  it  will 
recommend  itself  as  much  to  the  scientist  as  to 
the  breeder.  For  the  breeder,  when  desiring  to 
keep  his  varieties  up  to  their  standard,  or  when 
breeding  to  a  definite  idea,  obviously  keeps  his 
standard  and  his  ideal  for  the  whole  plant,  even 
if  he  breeds  only  for  flowers  or  for  fruit. 

I  have  chosen  the  color  of  the  purple  thorn- 
apple  as  a  first  example,  but  the  colors  of  other 
plants  show  so  many  diverging  aspects,  all 
pointing  so  clearly  to  the  same  conclusion,  that 
it  would  be  well  to  take  a  more  extensive  view 
of  this  interesting  subject. 

First  we  must  consider  the  correlation  in  the 
colors  of  flowers  and  fruits.  If  both  are  colored 
in  the  species,  whether  red  or  brown  or  purple 
or  nearly  black,  and  a  variety  lacking  this  hue 
is  known,  it  will  be  lacking  in  both  organs.  If 
the  color  is  pure,  the  flowers  and  berries  will  be- 
come white,  but  such  cases  are  rare.  Ordinar- 
ily a  yellowish  or  greenish  tinge  underlies  the 
ornamental  color,  and  if  this  latter  disappears, 
the  yellowish  ground  will  become  manifest.  So 
for  instance  in  the  Belladonna,  a  beautiful  per- 
ennial herb  with  great  shiny  black,  but  very 
poisonous,  fruits.     Its  flowers  are  brown,  but  in 


146  Retrograde  Varieties 

some  woods  a  variety  with  greenish  flowers  and 
bright  yellow  berries  occurs,  which  is  also  fre- 
quently seen  in  botanic  gardens.  The  anthocyan 
dye  is  lacking  in  both  organs,  and  the  same  is 
the  case  with  the  stems  and  the  leaves.  The 
lady's  laurel  or  Daphne  Mezereum  has  red  co- 
rollas, purple  leaves  and  red  fruits;  its  white- 
flowered  variety  may  be  distinguished  by  lack  of 
the  red  hue  in  the  stems  and  leaves,  and  by  their 
beautiful  yellow  berries.  Many  other  instances 
could  be  given,  since  the  loss  of  color  in  berries 
is  a  very  common  occurrence,  so  common  that 
for  instance,  in  the  heath-family  or  Ericaceae, 
with  only  a  few  exceptions,  all  berry-bearing 
species  have  white-fruited  varieties. 

The  same  correlation  is  observed  in  the  seeds. 
The  white-flowered  flax  may  be  seen  to  yield 
yellow  and  not  brown  seeds  as  in  the  blue  spe- 
cies. Many  varieties  of  flowers  may  be  recog- 
nized by  the  color  of  their  seeds,  as  in  the  pop- 
pies, stocks  and  others.  Other  white-flowered 
varieties  may  be  distinguished  when  germinat- 
ing, their  young  axes  being  of  a  pure  instead  of 
a  purplish  green.  It  is  a  test  ordinarily  used 
by  gardeners,  to  purify  their  flower  beds  long- 
before  the  blooming  time,  when  thinning  or 
weeding  them.  Even  in  wild  plants,  as  in 
Erodium,  Calluna,  Brunella  and  others,  a  bot- 
anist may   recognize   the   rare   white-flowered 


Retrograde  Varieties  147 

variety  by  the  pure  green  color  of  the  leaves, 
at  times  when  it  is  not  in  flower.  Some  sorts 
of  peas  bear  colored  flowers  and  a  red  mark  on 
the  stipules  of  their  leaves.  Among  bulbous 
plants  many  varieties  may  be  recognized  even 
in  the  dry  bulbs  by  the  different  tinges  of  the 
outer  scales. 

Leaving  the  colors,  we  come  now  to  another 
instance  of  correlation,  which  is  still  more  as- 
tonishing. For  it  is  as  rare,  as  color-varieties 
are  common.  It  is  afforded  by  some  plants  the 
leaves  of  which,  instead  of  being  entire  or 
only  divided  into  large  parts,  are  cleft  to  a 
greater  extent  by  repeated  fissures  of  the  mar- 
ginal lobes.  Such  foliar  variations  are  often 
seen  in  gardens,  where  they  are  cultivated  for 
their  beauty  or  singularity,  as  the  laciniated 
alders,  fern-leaved  beeches  and  limes,  oak- 
leaved  laburnums,  etc.  Many  of  them  are  de- 
scribed under  the  varietal  name  of  laciniata. 
In  some  cases  this  fissure  extends  to  the  petals 
of  the  flowers,  and  changes  them  in  a  way  quite 
analogous  to  the  aberrancy  of  the  leaves.  This 
is  known  to  occur  with  a  variety  of  brambles, 
and  is  often  seen  in  botanic  gardens  in  one  of 
the  oldest  and  most  interesting  of  all  anomalies, 
the  laciniated  variety  of  the  greater  celandine 
or  Chelidonium  majus.  Many  other  instances 
could  be  given.     Most  of  them  belong  to  the 


148  Retrograde  Varieties 

group  of  negative  variations,  as  we  have  defined 
them.  But  the  same  thing  occurs  also  with 
positive  varieties,  though  of  course,  such  cases 
are  very  rare.  The  best  known  instance  is  that 
of  the  ever-flowering  begonia,  Begonia  semper- 
florens,  which  has  green  leaves  and  white  flow- 
ers, but  which  has  produced  garden  varieties 
with  a  brown  foliage  and  pink  flowers.  Here 
also  the  new  quality  manifests  itself  in  different 
organs. 

Enough  has  now  been  said  on  correlative 
changes,  to  convince  us  that  they  are  as  a  rule 
to  be  considered  as  the  expression  of  some  gen- 
eral internal  or  physiologic  quality,  which  is  not 
limited  to  a  single  organ,  but  affects  all  parts 
of  the  organism,  provided  they  are  capable  of 
undergoing  the  change.  Such  characters  are 
therefore  to  be  considered  as  units,  and  should 
be  referred  to  the  group  of  single  characters. 

Opposed  to  these  are  the  true  compound  char- 
acters, which  consist  of  different  units.  These 
may  be  segregated  by  the  production  of  varie- 
ties, and  thereby  betray  the  separate  factors  of 
the  complex  group. 

The  most  beautiful  instances  of  such  complex 
characters  are  offered  by  the  colors  of  some  of 
the  most  prized  garden-flowers.  Rarely  these 
are  of  a  single  hue,  often  two  or  three  shades 
contribute  to  the  effect,  and  in  some  cases  spe- 


Retrograde  Varieties  149 

cial  spots  or  lines  or  tracings  are  to  be  seen  on  a 
white  or  on  a  colored  background.  That  such 
spots  and  lines  are  separate  units  is  obvious 
and  is  demonstrated  by  the  fact  that  some- 
times spotless  varieties  occur,  which  in  all  other 
respects  have  kept  the  colors  of  the  species. 
The  complexity  of  the  color  is  equally  evident, 
whenever  it  is  built  up  of  constituents  of  the 
anthocyan  and  of  the  yellow  group.  The  an- 
thocyan  dye  is  limited  to  the  sap-cavity  of  the 
cells,  while  the  yellow  and  pure  orange  colors 
are  tixed  in  special  organs  of  the  protoplasm. 
The  observation  under  the  microscope  shows  at 
once  the  different  units,  which  though  lying  in 
the  same  cell  and  in  almost  immediate  vicinity 
of  each  other  are  always  wholly  separated  from 
one  another  by  the  wall  of  the  vacuole  or  sap- 
filled  cell-cavity. 

The  combination  of  red  and  yellow  gives  a 
brown  tinge,  as  in^he  cultivated  wall-flower,  or 
those  bright  hues  of  a  dark  orange-red,  which 
are  so  much  sought  in  tulips.  By  putting  such 
flowers  for  a  short  time  in  boiling  water,  the 
cells  die  and  release  the  red  pigment,  which  be- 
comes diffused  in  the  surrounding  fluids  and  the 
petals  are  left  behind  with  their  yellow  tinge. 
In  this  way  it  is  easy  to  separate  the  constitu- 
ents, and  demonstrate  the  compound  nature  of 
the  original  colors. 


150  Retrograde  Varieties 

But  the  diversity  of  the  color  patterns  is  far 
from  being  exhausted  with  these  simple  in- 
stances. Apart  from  them,  or  joined  to  them, 
other  complications  are  frequently  seen,  which 
it  is  impossible  to  analyze  in  such  an  artificial 
way.  Here  we  have  to  return  to  our  former 
principle,  the  comparison  of  different  varieties. 
Assuming  that  single  units  may  be  lost,  ir- 
respective of  the  others,  we  may  expect  to  find 
them  segregated  by  variation,  wherever  a  suffi- 
ciently wide  range  of  color-varieties  is  in  culti- 
vation. In  fact,  in  most  cases  a  high  degree  of 
dissimilarity  may  be  reached  in  the  simplest 
way  by  such  a  separation  of  the  components, 
and  by  their  combination  into  most  diverse 
smaller  groups.  A  very  nice  instance  of  such 
an  analysis  of  flower-colors  is  afforded  by  the 
ordinary  snapdragon.  The  beautiful  brown- 
red  color  of  this  common  garden-plant  is  com- 
posed on  one  side  of  yellow  elements,  on  the 
other  of  red  units.  Of  the  yellow  there  are 
two,  one  staining  the  whole  corolla  with  a  light 
hue,  as  is  to  be  seen  in  the  pure  yellow  variety 
called  luteum.  This  form  has  been  produced 
by  the  loss  of  the  whole  group  of  the  red  con- 
stituents. If  the  yellow  tinge  is  also  lost,  there 
arises  a  white  variety,  but  this  is  not  absolutely 
colorless,  but  shows  the  other  yellow  constit- 
uent.    This  last  stains  only  some  small  parts 


Retrograde  Varieties  151 

of  the  lips  of  the  flower  around  the  throat, 
brightening,  as  it  seems,  the  entrance  for  the 
visiting  insects.  In  many  of  the  red  or  reddish 
varieties  this  one  yellow  patch  remains,  while 
the  general  yellow  hue  fails.  In  the  variety 
called  ^^  Brilliant  "  the  yellow  ground  makes 
the  red  color  more  shiny,  and  if  it  is  absent  the 
pure  carmine  tinge  predominates. 

It  is  readily  seen,  that  in  the  ordinary  form 
the  lips  are  of  a  darker  red  than  the  tube.  This 
evident  dissimilarity  indicates  some  complexity. 
iVnd  in  fact  we  have  two  varieties  which  exhibit 
the  two  causes  of  this  attribute  separately.  One 
of  them  is  called  ^'  Delila,"  and  has  the  red 
color  limited  to  the  lips,  whilst  the  tube  is  pure 
white.  The  other  is  called  ^  ^  Fleshy, ' '  and  is  of 
a  pale  pink  throughout  the  whole  corolla.  Ad- 
ding these  two  units  to  one  another,  we  get  the 
original  dark  red  of  the  wild  type,  and  it  may  be 
briefly  stated  here,  that  the  way  of  effecting 
such  an  addition  is  given  us  in  the  crossing  of 
the  ''  Fleshy  "  and  the  ''  Delila  "  variety, 
the  hybrid  showing  the  two  colors  and  return- 
ing thereby  to  the  old  prototype. 

Other  cases  of  compound  flower  colors  or  of 
color  patterns  might  be  given  as  in  the  Mimulus 
and  the  poppy,  and  in  most  of  these  cases  some 
varieties  are  to  be  seen  in  our  gardens  which 
show  only  the  single  constituents  of  the  group. 


152  Retrograde  Varieties 

Many  dark  flowers  have  an  intermediate  bright 
hued  form  besides  the  white  variety,  as  in  the 
case  of  roses,  asters,  Nicandra  and  so  on. 

Intermediate  forms  with  respect  to  stature 
may  also  be  seen.  The  opium-poppy,  the  snap- 
dragon, peas,  the  Nicandra,  and  many  other 
garden-plants  have  not  only  dwarf  varieties, 
but  also  some  of  intermediate  height.  These, 
though  they  are  intermediate  between  the  tall 
and  dwarf  types,  cannot  be  considered  as  transi- 
tions, as  between  them  and  the  extremes,  inter- 
mediates are,  as  a  rule  wholly  lacking.  In- 
stances of  the  same  occurrence  of  three  types 
may  be  seen  in  the  seeds  of  maize  (^'  Cuzco," 
'^  Horse-dent  "  and  ^^Gracillima")  of  beans  and 
some  other  plants.  The  Xanthium  Wootoni, 
above  referred  to,  with  only  part  of  the  prickles 
of  Xanthium  commune  is  also  a  very  curious  in- 
stance of  the  demonstration  of  the  compound 
nature  of  a  character. 

Summarizing  the  conclusions  that  may  be 
drawn  from  the  evidence  given  in  this  lecture, 
we  have  seen  that  varieties  differ  from  elemen- 
tary species  in  that  they  do  not  possess  anything 
really  new.  They  originate  for  the  greater  part 
in  a  negative  way,  by  the  apparent  loss  of  some 
quality,  and  rarely  in  a  positive  manner  by  ac- 
quiring a  character,  already  seen  in  allied  spe- 
cies.    These  characters  are  not  of  the  nature  of 


Retrograde  Varieties  153 

morphologic  entities,  but  are  to  be  considered 
as  physiologic  units,  present  in  all  parts  of  the 
organisms,  and  manifesting  themselves  where- 
ever  occasion  is  afforded.  They  are  units  in 
the  sense  that  they  may  appear  and  disappear 
singly.  But  very  often  they  are  combined  to 
yield  compound  characters,  which  are  capable 
of  analysis.  Opportunities  for  such  an  analysis 
are  afforded  by  these  groups  of  cultivated  va- 
rieties, of  which  some  members  show  a  single 
distinguishing  quality,  or  a  number  of  them. 


Lecture  VI 

STABILITY   AND   REAL   ATAVISM 

It  is  generally  believed  that  varieties  are 
principally  distinguished  from  species  by  their 
inconstancy.  This  conception  is  derived  from 
some  special  cases  and  transferred  to  others, 
and  in  its  common  form  this  belief  must  have 
originated  from  the  confusion  which  exists  as 
to  the  meaning  of  the  term  variety.  It  is 
true  that  vegetative  varieties  as  a  rule  run  back, 
when  propagated  by  seeds ;  they  are  an  obvious 
instance  of  inconstancy.  In  the  second  place 
we  have  considered  the  group  of  inconstant  or 
sporting  varieties,  which  of  course  we  must  ex- 
clude when  studying  the  stability  of  other  types. 
However,  even  these  sporting  varieties  are  un- 
stable only  to  a  certain  degree,  and  in  a  broader 
sense  will  prove  to  be  as  true  to  their  character 
as  the  most  constant  types. 

Having  separated  these  two  groups,  which 
include  also  the  wide  range  of  hybrid  forms,  we 
may  next  consider  only  those  varieties  of  pure 
origin,   and   ordinarily   propagated   by    seeds, 

154 


stability  and  Real  Atavism  155 

which  have  been  discussed  in  former  chapters. 
Their  general  character  lies  in  their  fidelity  to 
type,  and  in  the  fact  that  this  is  single,  and  not 
double,  as  in  the  sporting  varieties. 

But  the  current  belief  is,  that  they  are  only 
true  to  their  peculiarities  to  a  certain  degree, 
and  that  from  time  to  time,  and  not  rarely, 
they  revert  to  the  type  from  which  they  have 
arisen.  Such  reversion  is  supposed  to  prove 
that  they  are  mere  varieties,  and  at  the  same 
time  to  indicate  empirically  the  species  from 
which  they  have  sprung. 

In  the  next  lecture  we  shall  examine  critically 
the  evidence  on  which  this  assumption  rests. 
Before  doing  so  however,  it  will  be  necessary 
to  collate  the  cases  in  which  there  is  no  re- 
version at  all,  or  in  which  the  reversion  is  ab- 
sent at  least  in  experimental  and  pure  sowings. 

In  the  present  state  of  our  knowledge  it  is 
very  difficult  to  decide,  whether  or  not  true  re- 
version occurs  in  constant  varieties.  If  it  does 
occur,  it  surely  does  so  very  rarely  and  only 
under  unusual  circumstances,  or  in  particular 
individuals.  However  when  such  individuals 
are  multiplied  by  buds  and  especially  when  they 
are  the  only  representatives  of  their  type,  the 
reversion,  though  theoretically  rare,  will  be 
shown  by  nearly  every  specimen  of  the  va- 
riety.    Examples  of  this  will  be  given  below. 


156  Retrograde  Varieties 

They  are  generally  called  atavists  or  rever- 
sionists,  but  even  these  terms  are  sometimes 
used  in  a  different  sense. 

Lastly  it  is  to  be  said  that  the  empirical  and 
experimental  evidence  as  to  the  question  of  con- 
stancy is  not  as  extensive  as  it  should  be.  The 
experimental  conditions  are  seldom  described, 
and  it  is  only  recently  that  an  interest  in  the 
matter  has  been  awakened.  Much  remains  to 
be  done.  Among  other  things  the  innumerable 
varieties  of  trees,  shrubs  and  perennial  herbs 
should  be  tested  as  to  their  constancy  when 
grown  from  purely  fertilized  seeds.  Many  of 
them  may  be  included  among  the  number  that 
sport  constantly. 

Leaving  aside  the  doubtful  or  insufficiently 
studied  cases,  we  may  now  turn  our  attention  to 
the  facts  that  prove  the  absolute  stability  of 
a  large  number  of  varieties,  at  least  as  far  as 
such  completeness  can  be  attained  by  experi- 
ment or  observation. 

The  best  proof  is  afforded  by  the  varieties 
which  grow  wild  in  localities  where  they  are 
quite  isolated  from  the  species,  and  where  for 
this  reason,  no  possibility  of  crossing  disturbs 
the  significance  of  the  proof.  As  one  instance 
the  rayless  form  of  the  wild  camomile,  or  the 
Matricaria  Chamomilla  discoidea  may  be  men- 
tioned.   Many  systematists  have  been  so  strong- 


stability  and  Real  Atavism  157 

ly  impressed  with  its  absolute  constancy  and  its 
behavior  as  an  ordinary  species,  that  they  have 
elevated  it,  as  it  is  called,  to  the  rank  of  a  spe- 
cies. As  such  it  is  described  under  the  name  of 
Matricaria  discoidea  DC,  It  is  remarkable 
for  its  rapid  and  widespread  distribution,  as  of 
late  years  it  has  become  naturalized  in  different 
parts  of  America  and  of  Europe,  where  it  is  to 
be  seen  especially  in  France  and  in  Norway. 
Experimentally  I  raised  in  succeeding  years  be- 
tween 1000  and  2000  seedlings,  but  observed  no 
trace  of  reversion,  either  in  the  strongest  or  in 
the  numerous  very  small  and  weak  individuals 
which  appeared  in  the  cultures. 

The  tansy-ragwort  or  Senecio  Jacohaea  may 
be  chosen  as  a  second  instance.  It  is  a  per- 
ennial herb  with  short  rootstocks  and  stout 
stems  bearing  numerous  short-peduncled  heads 
in  a  large  compact  corymb;  it  multiplies  itself 
abundantlv  bv  seeds  and  is  very  common  on 
the  sand  dunes  of  Holland.  It  has  two  forms, 
differing  only  in  the  occurrence  or  the  lack  of 
the  ray  florets.  But  these  two  varieties  occupy 
different  localities  and  are  even  limited  to  dif- 
ferent provinces.  As  far  as  I  have  been  able  to 
ascertain  on  numerous  excursions  during  a 
series  of  years,  they  never  sport,  and  are  only 
intermingled  on  the  outskirts  of  their  habitats. 
The  rayless  form  is  generally  considered  as  the 


158  Retrograde  Varieties 

variety  but  it  is  quite  as  stable  as  the  radiate 
species. 

The  radiate  varieties  of  marigold,  quoted  in  a 
former  lecture,  seem  to  be  equally  constant, 
when  growing  far  away  from  their  prototypes. 
I  sowed  the  seeds  of  a  single  plant  of  the  radiate 
form  of  Bidens  cernua,  and  found  all  of  the 
seedlings  came  true,  and  in  the  next  year  I  had 
from  their  seed  between  2000  and  3000  flower- 
ing individuals,  all  equally  radiate.  Many 
species  of  composites  have  been  tried,  and  they 
are  all  constant.  On  the  other  hand  rare  sports 
of  this  kind  have  been  observed  by  Murr  and 
other  authors. 

Many  kinds  of  vegetables  and  of  fruits  give 
instances  of  stability.  White  strawberries, 
green  grapes,  white  currants,  crisped  lettuce, 
crisped  parsley  and  some  other  crisped  forms 
may  be  cited.  The  spinage  without  prickles  is 
a  widely  known  instance.  White-flowered  flax 
never  reverts  to  the  blue  prototype,  if  kept  pure. 
Sugar-peas  and  sugar-corn  afford  further  in- 
stances. Strawberries  without  runners  have 
come  true  from  seed  ever  since  their  first  ap- 
pearance, over  a  hundred  years  ago. 

Many  garden- varieties,  the  stability  of  which 
under  ordinary  circumstances  is  doubtful,  be- 
cause of  their  being  sown  too  close  to  other  va- 
rieties of  the  same  species,  have  been  tested  in 


stability  and  Real  Atavism  159 

respect  to  their  stability  by  different  writers 
and  at  different  times.  In  doing  this  it  is  plain 
that  it  is  very  essential  to  be  sure  of  the  purity 
of  the  seed.  Specimens  must  be  grown  in  posi- 
tions isolated  from  their  allies,  and  if  possible 
be  pollinated  artificially  with  the  exclusion  of 
the  visits  of  insects.  This  may  be  done  in  differ- 
ent ways.  If  it  is  a  rare  species,  not  cultivated 
in  the  neighborhood,  it  is  often  sufficient  to  make 
sure  of  this  fact.  Pollen  may  be  conveyed  by 
bees  from  distances  of  some  ten  or  twenty 
meters,  or  in  rare  cases  from  some  hundred 
meters  and  more,  but  a  greater  distance  is  or- 
dinarily sufficient  for  isolation.  If  the  flowers 
fertilize  themselves,  as  is  more  often  the  case 
than  is  generally  supposed,  or  if  it  is  easy  to 
pollinate  them  artificially,  with  their  own  pollen 
or  in  small  groups  of  similar  individuals,  the 
best  way  is  to  isolate  them  by  means  of  close 
coverings.  When  flowering,  the  plants  are  as  a 
rule  too  large  to  be  put  under  bell-glasses,  and 
moreover  such  coverings  would  keep  the  air 
moist,  and  cause  the  flower-buds  to  be  thrown 
off.  The  best  coverings  are  of  netting,  or  of 
canvas  of  sufficiently  wide  mesh,  although  after 
a  long  experience  I  greatly  prefer  cages  of 
fine  iron-wire,  which  are  put  around  and  over 
the  whole  plant  or  group  of  plants,  and  fastened 
securely  and  tightly  to  the  ground. 


160  Retrograde  Varieties 

Paper  bags  also  may  be  made  use  of.  They 
are  slipped  over  the  flowering  branches,  and 
bound  together  around  the  twigs,  thus  enclosing 
the  flowers.  It  is  necessary  to  use  prepared 
papers,  in  order  that  they  may  resist  rain 
and  wind.  The  best  sort,  and  the  one  that  I 
use  almost  exclusively  in  my  fertilization-ex- 
periments, is  made  of  parchment-paper.  This 
is  a  wood-pulp  preparation,  freed  artificially 
from  the  so-called  wood-substance  or  lignin. 
Having  covered  the  flowers  with  care,  and 
having  gathered  the  seeds  free  from  inter- 
mixtures and  if  possible  separately  for  each 
single  individual,  it  only  remains  to  sow  them 
in  quantities  that  will  yield  the  greatest  pos- 
sible number  of  individuals.  Reversions  are 
supposed  to  be  rare  and  small  groups  of  seed- 
lings of  course  would  not  suffice  to  bring  them 
to  light.  Only  sowings  of  many  hundreds  or 
thousands  of  individuals  are  decisive.  Such 
sowings  can  be  made  in  one  year,  or  can 
be  extended  over  a  series  of  years  and  of  gen- 
erations. Hildebrand  and  Hoffman  have  pre- 
ferred the  last  method,  and  so  did  Hof- 
meister  and  many  others.  Hildebrand  sowed 
the  white  hyacinth,  and  the  white  varieties  of 
the  larkspur,  the  stock  and  the  sweet  pea.  Hoff- 
man cultivated  the  white  flax  and  many  other 
varieties  and  Hofmeister  extended  his  sowings 


stability  and  Real  Atavism  161 

over  thirty  years  with  the  white  variety  of  the 
yellow  foxglove  {Digitalis  parviflora) . 

White-flowered  varieties  of  perennial  garden- 
plants  were  used  in  my  own  experiments.  I 
bought  the  plants,  flowered  them  under  isolation 
in  the  way  described  above,  gathered  the  seeds 
from  each  individual  separately  and  sowed  them 
in  isolated  groups,  keeping  many  hundreds  and 
in  some  cases  above  a  thousand  plants  up  to 
the  time  of  flowering.  Among  them  I  found 
only  one  inconstant  variety,  the  white  form  of 
the  yellow  columbine,  Aquilegia  chrysantha.  It 
evidently  belonged  to  the  group  of  sporting  va- 
rieties already  referred  to.  All  others  came  ab- 
solutely true  to  type  without  any  exception.  The 
species  experimented  with,  were  Campanula 
persicifolia,  Hyssopus  officinalis,  Lobelia  syphil- 
itica, Lychnis  chalcedonica,  Polemonium  dissec- 
tum.  Salvia  sylvestris  and  some  others.  Tested 
in  the  same  wav  I  found  the  white  varieties  of 
the  following  annual  plants  also  quite  true: 
Chrysanthemum  coronarium,  Godetia  amoena, 
Linum  usitatissimum.  Phlox  drummondi,  and 
Silene  Armeria.  To  these  may  be  added  the 
white  hemlock  stork's-bill  (Erodium  cicutarium 
album)  which  grows  very  abundantly  in  some 
parts  of  my  fatherland,  and  is  easily  recogniz- 
able by  its  pure  green  leaves  and  stems,  even 
when  not  flowering.  I  cultivated  it  in  large  num- 


162  Retrograde  Varieties 

bers  during  five  succeeding  generations,  but  was 
never  able  to  find  even  the  slightest  indication 
of  a  reversion  to  the  red  prototype.  The  scar- 
let pimpernel  or  Anagallis  arvensis  has  a  blue 
variety  which  is  absolutely  constant.  Even  in 
Britton  and  Brown's  "  Flora,"  which  rarel}^ 
enumerates  varieties,  it  is  mentioned  as  being 
probably  a  distinct  species.  Eight  hundred 
blooming  seedlings  were  obtained  from  isolated 
parents,  all  of  the  same  blue  color.  The  New 
Zealand  spinage  (Tetragonia  expansa)  has  a 
greenish  and  a  brownish  variety,  the  red  color 
extending  over  the  whole  foliage,  including  the 
stems  and  the  branches.  I  have  tried  both  of 
them  during  several  years,  and  they  never 
sported  into  each  other.  I  raised  more  than 
5000  seedlings,  from  the  different  seeds  of  one 
lot  of  the  green  variety  in  succeeding  years,  but 
neither  those  germinating  in  the  first  year,  nor 
the  others  coming  into  activity  after  two,  three 
or  four  years  of  repose  gave  any  sign  of  the 
red  color  of  the  original  species. 

It  is  an  old  custom  to  designate  intermediate 
forms  as  hybrids,  especially  when  both  the 
types  are  widely  known  and  the  intermediates 
rare.  Many  persons  believe  that  in  doing  so, 
they  are  giving  an  explanation  of  the  rarer 
forms.  But  since  the  laws  of  hybridism  are 
coming  to  be  known  we  shall  have  to  break  with 


stability  and  Real  Atavism  163 

all  such  usages.  So  for  instance  there  are  num- 
erous flowers  which  are  of  a  dark  red  or  a  dark 
blue  color,  and  which,  besides  a  white  variety, 
have  a  pink  or  a  pale  blue  form.  Such  pale 
varieties  are  of  exactly  the  same  value  as  others, 
and  on  testing  they  are  found  to  be  equally 
stable.  So  for  instance  the  pink  variety  of  the 
Sweet  William  {Silene  Armeria  rosea) ^  the 
Clarkia  pulchella  carnea  and  the  pale  variety 
of  the  corn-cockle,  called  usually  Agrostemma 
Githago  nicaeensis  or  even  simply  A.  nicaeensis. 
The  latter  variety  I  found  pure  during  ten  suc- 
ceeding generations.  Another  notable  stable 
intermediate  form  is  the  poppy  bearing  the 
Danish  flag  (Papaver  somniferum  Danebrog). 
It  is  an  old  variety,  and  absolutely  pure  when 
cultivated  separately.  A  long  list  of  other  in- 
stances might  easily  be  given. 

Many  garden-varieties,  that  are  still  univer- 
sally prized  and  cultivated  are  very  old.  It  is 
curious  to  note  how  often  such  forms  have  been 
introduced  as  novelties.  The  common  fox- 
glove is  one  of  the  best  examples.  It  has  a  mon- 
strous variety,  which  is  very  showy  because  it 
bears  on  the  summit  of  its  raceme  and  branches, 
large  erect  cup-shaped  flowers,  which  have  quite 
a  different  aspect  from  the  normal  thimble- 
shaped  side-blossoms.  These  flowers  are  or- 
dinarily described  as  belonging  to  the  anomaly 


164  Retrograde  Varieties 

known  as  "  peloria/'  or  regular  form  of  a 
normally  symmetric  type ;  they  are  large  and  ir- 
regular on  the  stems  and  the  vigorous  branches 
but  slender  and  quinate  on  the  weaker  twigs. 
Their  beauty  and  highly  interesting  anomalous 
character  has  been  the  cause  of  their  being  de- 
scribed many  times,  and  nearly  always  as  a 
novelty;  they  have  been  recently  re-introduced 
into  horticulture  as  such,  though  they  were  al- 
ready cultivated  before  the  middle  of  the  last 
century.  About  that  time  very  good  descrip- 
tions with  plates  were  published  in  the  journal 
^'  Flora  ''  by  Vrolik,  but  afterwards  they  seem 
to  have  been  forgotten.  The  peloric  variety 
of  the  foxglove  always  comes  true  from  seed, 
though  in  the  strict  sense  of  the  word  which 
we  have  chosen  for  our  discussion,  it  does  not 
seem  to  be  a  constant  and  pure  variety. 

It  is  very  interesting  to  compare  old  botani- 
cal books,  or  even  old  drawings  and  engravings 
containing  figures  of  anomalous  plants.  The 
celebrated  Pinacothec  of  Munich  contains  an 
old  picture  by  Holbein  (1495-1543)  representing 
St.  Sebastian  in  a  flower-garden.  Of  the  plants 
many  are  clearly  recognizable,  and  among 
others  there  is  one  of  the  *^  one-leaved  "  variety 
of  the  strawberry,  which  may  still  be  met 
with  in  botanical  gardens.  In  the  year 
1671  a  Dutch  botanist,  Abraham  Hunting  pub- 


Stability  and  Real  Atavism  165 

lished  a  large  volume  on  garden-plants,  con- 
taining a  great  number  of  very  good  engrav- 
ings. Most  of  them  of  course  show  normal 
plants,  but  intermixed  with  these  are  varieties, 
that  are  still  in  cultivation  and  therefore  must 
be  at  least  two  centuries  old.  Others,  though 
not  figured,  are  easily  recognized  by  their  names 
and  descriptions.  The  cockscomb  is  the  most 
widely  known,  but  many  white  or  double  flow- 
ered varieties  were  already  cultivated  at  that 
time.  The  striped  Jalappa,  the  crested  Sedum^ 
the  fasciated  crown-imperial,  white  strawber- 
ries, red  gooseberries  and  many  others  were 
known  to  Hunting. 

Some  varieties  are  as  old  as  culture  itself, 
and  it  is  generally  known  that  the  Eomans  cul- 
tivated the  white  form  of  the  opium-poppy  and 
used  the  foliage  of  the  red  variety  of  the  sugar- 
beet  as  a  vegetable. 

In  our  time  flowers  and  fruits  are  changing 
nearly  as  rapidly  as  the  fancies  and  tastes  of 
men.  Every  year  new  forms  are  introduced 
and  usurp  the  place  of  older  ones.  Many  are 
soon  forgotten.  But  if  we  look  at  old  country 
gardens,  a  goodly  number  of  fine  and  valued  old 
sorts  are  still  to  be  found.  It  would  be  worth 
while  to  make  special  collections  of  living  plants 
of  old  varieties,  which  surely  would  be  a  good 
and  interesting  work  and  bring  about  a  convic- 


166  Retrograde  Varieties 

tion  of  the  stability  of  pure  strainis.  Coming 
now  to  the  other  side  of  the  question,  we  may 
consider  those  cases  of  reversion  which  have 
been  recorded  from  time  to  time,  and  which  al- 
ways have  been  considered  as  direct  proofs  of 
the  varietal  character  of  the  reverting  form. 
Reversion  means  the  falling  back  or  returning 
to  another  type,  and  the  word  itself  expresses 
the  idea  that  this  latter  type  is  the  form  from 
which  the  variety  has  arisen. 

Some  instances  of  atavism  of  this  kind  are 
well  known,  as  they  are  often  repeated  by  in- 
dividuals that  are  multii^lied  by  buds  or  by 
grafting.  Before  looking  attentively  into  the 
different  features  of  the  many  cases  of  rare 
reversions  it  will  be  advisable  to  quote  a  few 
examples. 

The  flowering-currant  of  the  Pacific  Coast 
or  North  American  scarlet  ribes  {Ribes  san- 
giiineum),  a  very  popular  ornamental  shrub, 
will  serve  as  a  good  example.  It  is  prized  be- 
cause of  its  brilliant  red  racemes  of  flowers 
which  blossom  early  in  the  spring,  before  the  ap- 
pearance of  the  leaves.  From  this  species  a 
white  form  has  arisen,  which  is  an  old  and  wide- 
ly cultivated  one,  but  not  so  highly  prized  be- 
cause of  its  pale  flowers.  These  are  not  of  a 
pure  white,  but  have  retained  a  faint  reddish 
hue.     The  young  twigs  and  the  stalks  of  the 


Stahility  and^  Real  Atavism  167 

leaves  afford  an  instance  of  correlated  variabil- 
ity since  in  the  species  the  red  color  shows  it- 
self clearly  mixed  with  the  green,  while  in  the 
variety  this  tinge  is  wholly  wanting. 

Occasionally  this  white-flowered  currant  re- 
verts back  to  the  original  red  type  and  the  re- 
version takes  place  in  the  bud.  One  or  two 
buds  on  a  shrub  bearing  perhaps  a  thousand 
bunches  of  white  flowers  produce  twigs  and 
leaves  in  which  the  red  pigment  is  noticeable 
and  the  flowers  of  which  become  brightly  col- 
ored. If  such  a  twig  is  left  on  the  shrub,  it  may 
grow  further,  ramify  and  evolve  into  a  larger 
group  of  branches.  All  of  them  keep  true  to 
the  old  type.  Once  reverted,  the  branches  re- 
main forever  atavistic.  It  is  a  very  curious 
sight,  these  small  groups  of  red  branches  among 
the  many  white  ones.  And  for  this  reason  at- 
tention is  often  called  to  it,  and  more  than  once 
I  myself  have  had  the  opportunity  of  noting  its 
peculiarities.  It  seems  quite  certain  that  by 
planting  such  shrubs  in  a  garden,  we  may  rely 
upon  seeing  sooner  or  later  some  new  buds  re- 
verting to  the  prototype. 

Very  little  attention  seems  hitherto  to  have 
been  given  to  this  curious  phenomenon,  though 
in  many  respects  it  deserves  a  closer  investiga- 
tion. The  variety  is  said  to  have  originated 
from  seed  in  Scotland,  many  years  ago,  and 


168  Retrograde  Varieties 

seems  to  be  propagated  only  by  cuttings  or  by 
grafting.  If  this  is  true,  all  specimens  must  be 
considered  as  constituting  together  only  one 
individual,  notwithstanding  their  wide  distribu- 
tion in  the  gardens  and  parks  of  so  many  coun- 
tries. This  induces  me  to  suppose,  that  the 
tendency  to  reversion  is  not  a  character  of  the 
variety  as  such,  but  rather  a  peculiarity  of  this 
one  individual.  In  other  words  it  seems  prob- 
able that  when  the  whitish  variety  arises  a  sec- 
ond time  from  the  red  species,  it  is  not  at  all 
necessary  that  it  should  exhibit  this  same  tend- 
ency to  revert.  Or  to  put  it  still  in  another 
way,  I  think  that  we  may  suppose  that  a  variety, 
which  might  be  produced  repeatedly  from  the 
same  original  stock,  would  only  in  rare  indi- 
viduals have  a  tendency  to  revert,  and  in  most 
cases  would  be  as  absolutely  constant  as  the 
species  itself. 

Such  a  conception  would  give  us  a  distinct 
insight  into  the  cause  of  the  rarity  of  these 
reversions.  Many  varieties  of  shrubs  and  trees 
have  originated  but  once  or  twice.  Most  of 
them  must  therefore,  if  our  supposition  is  cor- 
rect, be  expected  to  be  stable  and  only  a  few 
may  be  expected  to  be  liable  to  reversions. 

Among  the  conifers  many  very  good  cases  of 
reversions  by  buds  are  to  be  found  in  gardens 
and  glasshouses.  They  behave  exactly  like  the 
whitish  currant.     But  as  the  varietal  characters 


Stability  and  Real  Atavism  169 

are  chiefly  found  in  the  foliage  and  in  the 
branches,  these  aberrations  are  to  be  seen  on 
the  plants  during  the  whole  year.  Moreover 
they  are  in  some  cases  much  more  numerous 
than  in  the  first  instance.  The  Cryptomeria  of 
Japan  has  a  variety  with  twigs  resembling 
ropes.  This  is  not  caused  by  a  twisting,  but 
only  by  a  curvature  of  the  needles  in  such  a  way 
that  they  seem  to  grow  in  spiral  lines  around 
the  twigs.  This  variety  often  reverts  to  the 
type  with  widely  spread,  straight  needles.  And 
on  many  a  specimen  four,  five,  or  more  reverted 
branches  may  be  seen  on  different  parts  of  the 
same  shrub.  Still  more  widely  cultivated  is  the 
shrub  called  Cephalotaxus  pedunculata  fasti- 
giata,  and  more  commonly  known  under  its  old 
name  of  Podocarpus  koraiana.  It  is  the  broom- 
like variety  of  a  species,  nearly  allied  to  the 
common  American  and  European  species  of 
yew,  (Taxus  minor  and  T.  haccata).  It  is  a  low 
shrub,  with  broadly  linear  leaves  of  a  clear 
green.  In  the  species  the  leaves  are  arranged  in 
two  rows,  one  to  the  left  and  one  to  the  right 
of  the  horizontally  growing  and  widely  spread- 
ing branches.  In  the  variety  the  branches  are 
erect  and  the  leaves  inserted  on  all  sides. 
When  sporting,  it  returns  to  the  bilateral  pro- 
totype and  flat  wings  of  fan-shaped  twigs  are 
produced  laterally  on  its  dense  broom-like  tufts. 


170  Retrograde  Varieties 

Wherever  this  variety  is  cultivated  the  same  re- 
version may  be  seen;  it  is  produced  abundant- 
ly, and  even  under  seemingly  normal  circum- 
stances. But  as  in  the  case  of  the  Ribes  all  the 
specimens  are  derived  by  buds  from  a  single 
original  jDlant.  The  variety  was  introduced 
from  Japan  about  the  year  1860,  but  is  prob- 
ably much  older.  Nothing  is  known  as  to  its 
real  origin.  It  never  bears  flowers  or  fruits. 
It  is  curious  to  note  that  the  analogous  variety 
of  the  European  yew,  Taxus  baccata  fastigiata, 
though  much  more  commonly  cultivated  than 
the  Ceplialotaxus,  never  reverts,  at  least  as  far 
as  I  have  been  able  to  ascertain.  This  clearly 
corroborates  the  explanation  given  above. 

After  considering  these  rare  instances  of 
more  widely  known  reversions,  we  may  now  ex- 
amine the  question  of  atavism  from  a  broader 
point  of  view.  But  in  doing  so  it  should  once 
more  be  remembered,  that  all  cases  of  hybrid- 
ism and  also  all  varieties  sporting  annually  or 
frequently,  are  to  be  wholly  excluded.  Only  the 
very  rare  occurrence  of  instances  of  atavism  in 
varieties  that  are  for  the  rest  known  to  be  ab- 
solutely constant,  is  to  be  considered. 

Atavism  or  reversion  is  the  falling  back  to  a 
prototype.  But  what  is  a  prototype?  We  may 
take  the  word  in  a  physiologic  or  in  a  systematic 
sense.     Physiologically   the    signification   is   a 


stability  and  Real  Atavism  171 

very  narrowly  restricted  one,  and  includes  only 
those  ancestors  from  which  a  form  is  known  to 
have  been  derived.  But  such  evidence  is  of 
course  historic.  If  a  variety  has  been  observed 
to  spring  from  a  definite  species,  and  if  the  cir- 
cumstances have  been  sufficiently  ascertained 
not  to  leave  the  slightest  doubt  as  to  its  pure 
origin,  and  if  moreover  all  the  evidence  has 
been  duly  recorded,  we  may  say  that  the  origin 
of  the  variety  is  historically  known.  In  most 
cases  we  must  be  content  with  the  testimony, 
given  somewhat  later,  and  recorded  after  the 
new  variety  had  the  opportunity  of  showing 
its  greater  merits. 

If  it  now  happens  that  such  a  variety  of  re- 
corded origin  should  occasionally  revert  to  its 
parent-species,  we  have  all  we  can  wish  for,  in 
the  way  of  a  thoroughly  proved  case  of  atavism. 
But  such  instances  are  very  rare,  as  the  birth 
of  most  varieties  has  only  been  very  imper- 
fectly controlled. 

Next  to  this  comes  the  systematic  relation  of 
a  variety  to  its  species.  The  historic  origin  of 
the  variety  may  be  obscure,  or  may  simply  be 
forgotten.  But  the  distinguishing  marks  are 
of  the  order  described  in  our  last  lecture,  either 
in  the  positive  or  in  the  negative  direction,  and 
on  this  ground  the  rarer  form  is  considered  to 
be  a  variety  of  the  more  wide-spread  one.     If 


172  Retrograde  Varieties 

now  the  presumed  variety  sports  and  runs  over 
to  the  presumed  type,  the  probability  of  the 
supposed  relation  is  evidently  enhanced.  But 
it  is  manifest  that  the  explanation  rests  upon 
the  results  of  comparative  studies,  and  not 
upon  direct  observations  of  the  phenomena 
themselves. 

The  nearer  the  relations  between  the  two 
types  in  question,  the  less  exposed  to  doubt  and 
criticism  are  the  conclusions.  But  the  domain 
of  atavism  is  not  restricted  to  the  cases  de- 
scribed. Quite  on  the  contrary  the  facts  that 
strike  us  most  forcibly  as  being  reversions  are 
those  that  are  apt  to  give  us  an  insight  into  the 
systematic  affinity  of  a  higher  degree.  We  are 
disposed  to  make  use  of  them  in  our  attempts 
to  perfect  the  natural  system  and  to  remould 
it  in  such  a  way  as  to  become  a  pedigree  of  the 
related  groups.  Such  cases  of  atavism  no 
doubt  occur,  but  the  anomalies  referred  to  them 
must  be  interpreted  merely  on  the  ground  of  our 
assumptions  as  to  the  relative  places  in  the  sys- 
tem to  be  assigned  to  the  different  forms. 

Though  such  instances  cannot  be  considered 
as  belonging  strictly  to  the  subject  we  are  deal- 
ing with,  I  think  it  may  be  as  well  to  give  an  ex- 
ample, especially  as  it  affords  an  occasion  for 
referring  to  the  highly  important  researches  of 
Heinricher    on    the    variability    and    atavistic 


stability  and  Real  Atavism  173 

tendencies  of  the  pale  blue  flag  or  Iris  pallida. 
The  flowers  of  the  blue  flags  have  a  perianth 
of  six  segments  united  below  into  a  tube.  The 
three  outer  parts  are  dilated  and  spreading,  or 
reflexed,  while  the  three  inner  usually  stand 
erect,  but  in  most  species  are  broad  and  colored 
like  the  outer  ones.  Corresponding  to  the  outer 
perianth-segments  are  the  three  stamens  and 
the  three  petal-like  divisions  of  the  style,  each 
bearing  a  transverse  stigma  immediately  above 
the  anther.  They  are  pollinated  by  humble-bees, 
and  in  some  instances  by  flies  of  the  genus 
Rhingia,  which  search  for  the  honey,  brush  the 
pollen  out  of  the  anthers  and  afterwards  de- 
posit it  on  the  stigma.  According  to  systematic 
views  of  the  monocotyledons  the  original  proto- 
type of  the  genus  Iris  must  have  had  a  whorl  of 
six  equal,  or  nearly  equal  perianth-segments 
and  six  stamens,  such  as  are  now  seen  in  the 
more  primitive  types  of  the  family  of  the  lilies, 
as  for  instance  in  the  lilies  themselves,  the 
tulips,  hyacinths  and  others.  As  to  the 
perianth  this  view  is  supported  by  the 
existence  of  one  species,  the  Iris  falcifolia, 
the  perianth  of  which  consists  of  six  equal 
parts.  But  species  with  six  stamens  are 
wholly  lacking.  Heinricher  however,  in  culti- 
vating some  anomalous  forms  of  Iris  pallida, 
succeeded  in  filling  out  this  gap  and  in  produc- 


174  Retrograde   Varieties 

ing  flowers  with  a  uniform  perianth  and  six 
stamens,  recalling  thereby  the  supposed  ances- 
tral type.  The  way  in  which  he  got  these  was 
as  follows:  he  started  from  some  slight  devia- 
tions observed  in  the  flowers  of  the  pale  spe- 
cies, sowed  the  seeds  in  large  numbers  and  se- 
lected from  the  seedlings  only  those,  which 
clearly  showed  anomalies  in  the  expected 
atavistic  direction.  By  repeating  this  during 
several  generations  he  at  last  reached  his  goal 
and  was  able  to  give  reality  to  the  prototype, 
which  formerly  was  only  a  hypothetical  one. 
The  Iris  kaempferi,  a  large-flowered  Japanese 
species  much  cultivated  in  gardens,  is  very  vari- 
able in  the  number  of  the  different  parts  of  its 
flowers,  and  may  in  some  instances  be  seen  even 
with  six  stamens.  If  studied  in  the  same  way  as 
Heinricher's  iris,  it  no  doubt  will  yield  highly 
interesting  and  confirmatory  results. 

Many  other  instances  of  such  systematic  atav- 
ism could  be  given,  and  every  botanist  can  easily 
add  some  from  memory.  Many  anomalies,  oc- 
curring spontaneously,  are  evidently  due  to  the 
same  principle,  but  it  would  take  too  long  to 
describe  them. 

Reversion  may  occur  either  by  buds  or  by 
seeds.  It  is  highly  probable  that  it  occurs  more 
readily  by  sexual  than  by  asexual  propagation. 
But  if  we  restrict  the  discussion  to  the  limits 


stability  and  Real  Atavism  175 

hitherto  observed,  seed-reversions  must  be  said 
to  be  extremely  rare.  Or  rather  cases  which 
are  sufficiently  certain  to  be  relied  upon,  are 
very  rare,  and  perhaps  wholly  lacking.  Most 
of  the  instances,  recorded  by  various  writers, 
are  open  to  question.  Doubts  exist  as  to  the 
purity  of  the  seeds  and  the  possibility  of  some 
unobserved  cross  disturbing  the  results. 

In  the  next  lecture  we  shall  deal  in  general 
with  the  ordinary  causes  and  results  of  such 
crosses.  We  shall  then  see  that  they  are  so 
common  and  occur  so  regularly  under  ordinary 
circumstances  that  we  can  never  relv  on  the 
absolute  purity  of  any  seeds,  if  the  impossibility 
of  an  occasional  cross  has  not  been  wholly  ex- 
cluded, either  by  the  circumstances  themselves, 
or  by  experimental  precautions  taken  during 
the  flowering  period. 

For  these  reasons  cases  of  atavism  given 
without  recording  the  circumstances,  or  the  pre- 
cautions that  guarantee  the  purity  of  the  fertili- 
zation, should  always  be  disregarded.  And 
moreover  another  proof  should  always  be  de- 
manded. The  parent  which  yielded  the  seeds 
might  be  itself  a  hybrid  and  liable  to  reversions 
by  the  ordinary  laws  of  the  splitting  up  of  hy- 
brids. Such  cases  should  likewise  be  discarded, 
since  they  bring  in  confusing  elements.  If  we 
review  the  long  list  of  recorded  cases  by  these 


176  Retrograde  Varieties 

strict  methods  of  criticism  very  few  instances 
will  be  found  that  satisfy  legitimate  demands. 
On  this  ground  it  is  by  far  safer  in  the  present 
state  of  our  knowledge,  to  accept  bud-variations 
only  as  direct  proofs  of  true  atavism.  And 
even  these  may  not  always  be  relied  on,  as  some 
hybrids  are  liable  to  split  up  in  a  vegetative 
way,  and  in  doing  so  to  give  rise  to  bud-varia- 
tions that  are  in  many  respects  apparently  sim- 
ilar to  cases  of  atavism.  But  fortunately  such 
instances  are  as  yet  very  rare. 

After  this  discussion  it  would  be  bold  indeed 
to  give  instances  of  seed-atavism,  and  I  believe 
that  it  will  be  better  to  refrain  wholly  from  do- 
ing so. 

Many  instances  of  so-called  atavism  are  of 
purely  morphologic  nature.  The  most  interest- 
ing cases  are  those  furnished  by  the  forms 
which  some  plants  bear  only  while  young,  and 
which  evidently  connect  them  with  allied  species, 
in  which  the  same  features  may  be  seen  in  the 
adult  state.  Some  species  of  the  genus  Acacia 
bear  bipinnate  leaves,  while  others  have  no 
leaves  at  all,  but  bear  broadened  and  flattened 
petioles  instead.  The  second  type  is  presumed 
to  be  descended  from  the  first  by  the  loss 
of  the  leaflets  and  the  modification  of  the  stalks 
into  flat  and  simple  phyllodes.  But  many  of 
them  are  liable  to  recall  this  primitive  form 


Stability  and  Real  Atavism  111 

when  very  young,  in  the  first  two  or  three,  or 
sometimes  in  eight  or  ten  primary  leaves. 
These  leaves  are  small  because  of  the  weakness 
of  the  young  plant  and  therefore  often  more  or 
less  reduced  in  structure.  But  they  are  usually 
strictly  bipinnate  and  thereby  give  testimony 
as  to  their  descent  from  species  which  bear  such 
leaves  throughout  their  life. 

Other  similar  cases  could  be  given,  but  this 
will  suffice.  They  once  more  show  how  neces- 
sary it  is  to  separate  the  different  cases,  thrown 
together  until  now,  under  this  general  name  of 
atavism.  It  would  be  far  better  to  give  them 
all  special  names,  and  as  long  as  these  are  not 
available  we  must  be  cautious  not  to  be  mis- 
guided by  the  name,  and  especially  not  to  con- 
fuse different  phenomena  with  one  another,  be- 
cause at  the  present  time  they  bear  the  same 
names. 

Taking  into  consideration  the  relatively  nu- 
merous restrictions  resulting  from  this  discus- 
sion, we  will  now  make  a  hasty  survey  of  some 
of  the  more  notable  and  generally  acknowledged 
cases  of  atavism  by  bud-propagation.  But  it 
should  be  repeated  once  more  that  most  of  the 
highly  cultivated  plants,  grown  as  vegetables  or 
for  their  fruit  or  flowers,  have  so  many  crosses 
in  their  ancestry,  that  it  seems  better  to  exclude 
them  from  all  considerations,  in  which  purity  of 


1^8  Retrograde  Varieties 

descent  is  a  requisite.  By  so  doing,  we  exclude 
most  of  the  facts  which  were  until  now  gener- 
ally relied  upon.  For  the  roses,  the  hyacinths, 
the  tulips,  the  chrysanthemums  always  have 
furnished  the  largest  contributions  to  the  dem- 
onstrations of  bud-variation.  But  they  have 
been  crossed  so  often,  that  doubt  as  to  the  purity 
of  the  descent  of  any  single  form  may  recur, 
and  may  destroy  the  usefulness  of  their  many 
recorded  cases  of  bud- variation  for  the  demon- 
stration of  real  atavism.  The  same  assertion 
holds  good  in  many  other  cases,  as  with  Azalea 
and  Camellia.  And  the  striped  varieties  of 
these  genera  belong  to  the  group  of  ever-sport- 
ing forms,  and  therefore  will  be  considered 
later  on.  So  it  is  with  carnations  and 
pinks,  which  occasionally  vary  hj  layering,  and 
of  which  some  kinds  are  so  uncertain  in  char- 
acter that  they  are  called  by  floriculturists 
'*  catch-flowers."  On  the  other  hand  there  is 
a  larger  group  of  cases  of  reversion  by  buds, 
which  is  probably  not  of  hybrid  nature,  nor  due 
to  innate  inconstancy  of  the  variety,  but  must 
be  considered  as  pure  atavism.  I  refer  to  the 
bud-variations  of  so  many  of  our  cultivated 
varieties  of  shrubs  and  trees.  Many  of  them 
are  cultivated  because  of  their  foliage.  They 
are  propagated  by  grafting,  and  in  most  cases 
it  is  probable  that  all  the  numerous  specimens 


stability  and  Real  Atavism  179 

of  the  same  variety  have  been  derived  in  this 
way  from  one  primitive,  aberrant  individual. 
We  may  disregard  variegated  leaves,  spotted  or 
marked  with  white  or  yellow,  because  they  are 
too  inconstant  types. 

We  may  next  turn  our  attention  to  the  va- 
rieties of  trees  with  cut  leaves,  as  the  oak- 
leaved  Laburnum,  the  parsley-leaved  vine  and 
the  fern-leaved  birch.  Here  the  margin  of  the 
leaves  is  deeply  cut  and  divided  by  many 
incisions,  which  sometimes  change  only  the 
outer  parts  of  the  blade,  but  in  other  cases  may 
go  farther  and  reach,  or  nearly  reach,  the  mid- 
vein,  and  change  the  simple  leaf  into  a  seem- 
ingly compound  structure.  The  anomaly  may 
even  lead  to  the  almost  complete  loss  of  all  the 
chorophyll-tissue  and  the  greater  part  of  the 
lateral  veins,  as  in  the  case  of  the  cut-leaved 
beech  or  Fagus  sylvatica  pectinata. 

Such  varieties  are  often  apt  to  revert  by  buds 
to  the  common  forms.  The  cut-leaved  beech 
sometimes  reverts  partially  only,  and  the 
branches  often  display  the  different  forms  of 
cut-leaved,  fern-like,  oak-leaved  and  other  vari- 
ously shaped  leaves  on  the  same  twigs.  But 
this  is  merely  due  to  the  wide  variability  of  the 
degree  of  fissure  and  is  to  be  considered  only  as 
a  fluctuation  between  somewhat  widely  distant 
extremes,  which  may  even  apparently  include 


180  Retrograde  Varieties 

the  form  of  the  common  beech-leaves.  It  is  not 
a  bud-variation  at  all,  and  it  is  to  be  met  with 
quite  commonly  while  the  true  reversions  by 
buds  are  very  rare  and  are  of  the  nature  of 
sports  appearing  suddenly  and  remaining  con- 
stant on  the  same  twig.  Analogous  phenomena 
of  wide  variability  with  true  reversion  may  be 
seen  in  the  variety  of  the  European  hornbeam 
called  Carpinus  Betnlus  heteropliylla.  The 
leaves  of  this  tree  generally  show  the  greatest 
diversity  in  form.  Some  other  cases  have  been 
brought  together  by  Darwin.  In  the  first  place 
a  subvariety  of  the  weeping-willow  with  leaves 
rolled  up  into  a  spiral  coil.  A  tree  of  this  kind 
kept  true  for  twenty-five  years  and  then  threw 
out  a  single  upright  shoot  bearing  flat  leaves. 
The  barberry  {Berheris)  offers  another  case; 
it  has  a  well  known  variety  with  seedless  fruit, 
which  can  be  propagated  by  cuttings  or  layers, 
but  its  runners  are  said  always  to  revert  to  the 
common  form,  and  to  produce  ordinary  berries 
with  seeds.  Most  of  the  cases  referred  to  by 
Darwin,  however,  seem  to  be  doubtful  and  can- 
not be  considered  as  true  proofs  of  atavism  until 
more  is  known  about  the  circumstances  under 
which  they  were  produced. 

Red  or  brown-leaved  varieties  of  trees  and 
shrubs  also  occasionally  produce  green-leaved 
branches,  and  in  this  way  revert  to  the  type 


stability  and  Real  Atavism  181 

from  which  they  must  evidently  have  arisen. 
Instances  are  on  record  of  the  hazel,  Corylus 
Avellana,  of  the  allied  Corylus  tubulosa,  of 
the  red  beech,  the  brown  birch  and  of  some  other 
purple  varieties.  Even  the  red  bananas,  which 
bear  fruits  without  seeds  and  therefore  have  no 
other  way  of  being  propagated  than  by  buds, 
have  produced  a  green  variety  with  yellow 
fruits.  The  Hortensia  of  our  gardens  is  an- 
other instance  of  a  sterile  form  which  has  been 
observed  to  throw  out  a  branch  with  cymes 
bearing  in  their  center  the  usual  small  stam- 
inate  and  pistillate  flowers  instead  of  the  large 
radiate  and  neutral  corollas  of  the  variety, 
thereby  returning  to  the  original  wild  type. 
Crisped  weeping- willows,  crisped  parsley  and 
others  have  reverted  in  a  similar  manner. 

All  such  cases  are  badly  in  need  of  a 
closer  investigation.  And  as  they  occur  only 
occasionally,  or  as  it  is  commonlj^  stated,  by  ac- 
cident, the  student  of  nature  should  be  prepared 
to  examine  carefully  any  case  which  might  pre- 
sent itself  to  him.  Many  phases  of  this  difficult 
problem  could  no  doubt  be  solved  in  this  way. 
First  of  all  the  question  arises  as  to  whether  the 
case  is  one  of  real  atavism,  or  is  only  seemingly 
so,  being  due  to  hybrid  or  otherwise  impure  de- 
scent of  the  varying  individual,  and  secondly 
whether  it  may  be  only  an  instance  of  the  regu- 


182  Retrograde  Varieties 

larly  occurring  so-called  atavism  of  the  sporting 
varieties  with  which  we  shall  deal  in  a  later 
lecture.  If  it  proves  to  be  real  atavism 
and  rare,  the  case  should  be  accurately 
described  and  figured,  or  photographed  if  pos- 
sible; and  the  exact  position  of  the  reverting 
bud  should  be  ascertained.  Very  likely  the  so- 
called  dormant  or  resting  buds  are  more  liable 
to  reversions  than  the  primary  ones  in  the  axils 
of  the  leaves  of  young  twigs.  Then  the  char- 
acters of  the  atavistic  branches  should  be  mi- 
nutely compared  with  those  of  the  presumed  an- 
cestor ;  they  may  be  quite  identical  with  them  or 
slightly  divergent,  as  has  been  asserted  in  some 
instances.  The  atavism  may  be  complete  in  one 
case,  but  more  or  less  incomplete  in  others. 

By  far  the  most  interesting  point  is  the  ques- 
tion, as  to  what  is  to  be  expected  from  the  seeds 
of  such  an  atavistic  branch.  Will  they  keep 
true  to  the  reverted  character,  or  return  to  the 
characters  of  the  plant  which  bears  the  retro- 
grade branch?  Will  all  of  them  do  so,  or  only 
part  of  them,  and  how  large  a  part  ?  It  is  very 
astonishing  that  this  question  should  still  be 
unsolved  where  so  many  individual  trees  bear 
atavistic  branches  that  remain  on  them  through 
long  series  of  years.  But  then  many  such 
branches  do  not  flower  at  all,  or  if  they  flower 
and  bear   seed,   no   care  is   taken   to  prevent 


stability  and  Real  Atavism  183 

cross-fertilization  with  the  other  flowers  of  the 
same  plant,  and  the  results  have  no  scientific 
value.  For  anyone  who  cares  to  work  with 
the  precautions  prescribed  by  science,  a  wide 
field  is  here  open  for  investigation,  because  old 
reverted  branches  may  be  met  with  much  less 
rarely  than  new  ones. 

Finally  the  possibility  is  always  to  be  con- 
sidered that  the  tendency  to  bud-reversions  may 
be  a  special  feature  of  some  individuals,  and 
may  not  be  met  with  in  others  of  the  same 
variety.  I  have  spoken  of  this  before.  For  the 
practical  student  it  indicates  that  a  specimen, 
once  observed  to  produce  atavistic  buds,  may  be 
expected  to  do  the  same  thing  again.  And  then 
there  is  a  very  good  chance  that  by  combining 
this  view  with  the  idea  that  dormant  buds  are 
more  apt  to  revert  than  young  ones,  we  may  get 
at  a  method  for  further  investigation,  if  we  re- 
cur to  the  practice  of  pruning.  By  cutting 
away  the  young  twigs  in  the  vicinity  of  dormant 
buds,  we  may  incite  these  to  action.  Evidently 
we  are  not  to  expect  that  in  so  doing  they  will 
all  become  atavistic.  For  this  result  is  not  at 
all  assured;  on  the  contrary,  all  that  we  might 
hope  to  attain  would  be  the  possibility  of  some 
of  them  being  induced  to  sport  in  the  desired 
direction. 

Many  questions  in  scientific  research  can  only 


184  Retrograde  Varieties 

be  answered  by  long  and  arduous  work  in  well- 
equipped  laboratories;  they  are  not  to  be  at- 
tempted by  every  one.  But  there  are  other 
problems  which  the  most  complete  of  institu- 
tions are  not  able  to  study  if  opportunity  is  not 
offered  them,  and  such  opportunities  are  apt  to 
occur  more  often  in  fields,  gardens,  parks, 
woods  and  plains,  than  in  the  relatively  small 
experimental  gardens  of  even  the  largest  in- 
stitution. Therefore,  whosoever  has  the  good 
fortune  to  find  such  sports,  should  never  allow 
the  occasion  to  pass  without  making  an  investi- 
gation that  may  bring  results  of  very  great  im- 
portance to  science. 


Lecture  VII 

FALSE   ATAVISM    OR   VICINISM 

About  the  middle  of  the  last  century  Louis 
de  Vilmorin  showed  that  it  was  possible  to 
subject  plants  to  the  methods  of  ameliora- 
tion of  races  then  in  use  for  domestic  animals, 
and  since  that  time  atavism  has  played  a  large 
part  in  all  breeding-processes.  It  was  consid- 
ered to  be  the  greatest  enemy  of  the  breeder, 
and  was  generally  spoken  of  as  a  definite  force, 
working  against  and  protracting  the  endeav- 
ors of  the  horticulturist. 

No  clear  conception  as  to  its  true  nature  had 
been  formulated,  and  even  the  propriety  of 
designating  the  observed  phenomena  by  the 
term  atavism  seemed  doubtful.  Duchesne 
used  this  word  some  decades  ago  to  designate 
those  cases  in  which  species  or  varieties  revert 
spontaneously,  or  from  unknown  internal 
causes,  to  some  long-lost  characters  of  their  an- 
cestors. Duchesne's  definition  was  evidently  a 
sharp  and  useful  one,  since  it  developed  for  the 
first  time  the  idea  of  latent  or  dormant  qualities, 

185 


186  Retrograde  Varieties 

formerly  active,  and  awaiting  probably  through 
centuries  an  occasion  to  awaken,  and  to  dis- 
play the  lost  characters. 

Cases  of  apparent  reversion  were  often  seen 
in  nurseries,  especially  in  flower  culture,  which 
under  ordinary  circumstances  are  rarely 
wholly  pure,  but  always  sport  more  or  less  into 
the  colors  and  forms  of  allied  varieties.  Such 
sporting  individuals  have  to  be  extirpated 
regularly,  otherwise  the  whole  variety  would 
soon  lose  its  type  and  its  uniformity  and  run 
over  to  some  other  form  in  cultivation  in  the 
vicinitv.  For  this  reason  atavism  in  nurseries 
causes  much  care  and  labor,  and  consequently 
is  to  be  dealt  with  as  a  very  important  factor. 

From  time  to  time  the  idea  has  suggested 
itself  to  some  of  the  best  authorities  on  the 
amelioration  of  plants,  that  this  atavism  was 
not  due  to  an  innate  tendency,  but,  in  many 
cases  at  least,  was  produced  by  crosses  between 
neighboring  varieties.  It  is  especially  owing 
to  Verlot  that  this  side  of  the  question  was 
brought  forward.  But  breeders  as  a  rule  have 
not  attached  much  importance  to  tliis  supposi- 
tion, chiefly  because  of  the  great  practical  diffi- 
culties attending  any  attempt  to  guard  the  spe- 
cies of  the  larger  cultures  against  intermixture 
with  other  varieties.  Bees  and  humble-bees  fly 
from  bud  to  bud,  and  carry  the  pollen  from  one 


False  Atavism  187 

sort  to  another,  and  separation  by  great  dis- 
tances would  be  required  to  avoid  this  source  of 
impurity.  Unfortunately  the  arrangements 
and  necessities  of  large  cultures  make  it  impos- 
sible to  isolate  the  allied  varieties  from  each 
other. 

From  a  theoretical  point  of  view  the  origin 
of  these  impurities  is  a  highly  important  ques- 
tion. If  the  breeders'  atavism  is  due  to  crosses, 
and  only  to  this  cause,  it  has  no  bearing  at  all 
on  the  question  of  the  constancy  of  varieties. 
And  the  general  belief,  that  varieties  are  dis- 
tinguished from  true  species  by  their  repeated 
reversion  and  that  even  such  reversibility  is  the 
real  distinction  of  a  variety,  would  not  hold. 

For  this  reason  I  have  taken  much  trouble 
in  ascertaining  the  circumstances  which  attend 
this  form  of  atavism.  I  have  visited  a  number 
of  the  leading  nurseries  of  Europe,  tested  their 
products  in  various  ways,  and  made  some  ex- 
periments on  the  unavoidable  conditions  of 
hybridizing  and  on  their  effect  on  the  ensuing 
generations.  These  investigations  have  led  me 
to  the  conclusion,  that  atavism,  as  it  is  gener- 
ally described,  always  or  nearly  always  is  due 
to  hybridization,  and  therefore  it  is  to  be  con- 
sidered as  untrue  or  false  atavism. 

True  atavism,  or  reversion  caused  by  an  in- 
nate latent  tendency,  seems  to  be  very  rare. 


188  Retrograde  Varieties 

and  limited  to  such  cases  as  we  have  spoken  of 
under  our  last  heading.  And  since  the  defi- 
nition, given  to  this  term  by  its  author,  Du- 
chesne, is  generally  accepted  in  scientific  works, 
it  seems  better  not  to  use  it  in  another  sense, 
but  rather  to  replace  it  in  such  cases  by  another 
term.  For  this  purpose  I  propose  the  word 
vicinism,  derived  from  the  Latin  vicinus  or 
neighbor,  as  indicating  the  sporting  of  a  variety 
under  the  influence  of  others  in  its  vicinity. 
Used  in  this  way,  this  term  has  the  same  bear- 
ing as  the  word  atavism  of  the  breeders,  but 
it  has  the  advantage  of  indicating  the  true  cause 
thereof. 

It  is  well  known  that  the  term  variability  is 
commonly  employed  in  the  broadest  possible 
sense.  No  single  phenomenon  can  be  desig- 
nated by  this  name,  unless  some  primary  re- 
striction be  given.  Atavism  and  vicinism  are 
both  cases  of  variability,  but  in  wholly  different 
sense.  For  this  reason  it  may  be  as  well,  to 
insert  here  a  short  survey  of  the  general  mean- 
ings to  be  conveyed  by  the  term  variation.  It 
implies  in  the  first  place  the  occurrence  of  a 
wide  range  of  forms  and  tj^oes,  irrespective  of 
their  origin,  and  in  the  second  place  the  process 
of  the  change  in  such  forms.  In  the  first  signifi- 
cation it  is  nearly  identical  with  polymorphy, 
or  richness  of  types,  especially  so  when  these 


False  Atavism  189 

types  are  themselves  quite  stable,  or  when  it  is 
not  at  all  intended  to  raise  the  question  of  their 
stability.  In  scientific  works  it  is  commonly 
used  to  designate  the  occurrence  of  subspecies 
or  varieties,  and  the  same  is  the  case  in  the 
ordinary  use  of  the  term  when  dealing  with 
cultivated  plants.  A  species  may  consist  of 
larger  or  smaller  groups  of  such  units,  and 
they  may  be  absolutely  constant,  never  sport- 
ing if  hybridization  is  precluded,  and  neverthe- 
less it  may  be  called  highly  variable.  The 
opium-poppy  affords  a  good  instance.  It 
''  varies  ''  in  height,  in  color  of  foliage  and 
flowers ;  the  last  are  often  double  or  laciniated ; 
it  may  have  white  or  bluish  seeds,  the  capsules 
may  open  themselves  or  remain  closed  and  so 
on.  But  every  single  variety  is  absolutely  con- 
stant, and  never  runs  into  another,  when  the 
flowers  are  artificially  pollinated  and  the  visits 
of  insects  excluded.  So  it  is  with  many  other 
species.  They  are  at  the  same  time  wholly 
stable  and  very  variable. 

The  terms  variation  and  variety  are  used 
frequently  when  speaking  of  hybrids.  By  cross- 
ing forms,  which  are  already  variable  in  the 
sense  just  mentioned,  it  is  easy  to  multiply  the 
number  of  the  types,  and  even  in  crossing  pure 
forms  the  different  characters  may  be  combined 
in  different  ways,  the  resulting  combinations 


190  Retrograde  Varieties 

yielding  new,  and  very  often,  valuable  varieties. 
But  it  is  manifest  that  this  form  of  variation 
is  of  quite  another  nature  from  the  variations 
of  pure  races.  Many  hybrid  varieties  are  quite 
constant,  and  remain  true  to  their  type  if  no 
further  crosses  are  made ;  many  others  are  arti- 
ficially propagated  only  in  a  vegetative  way, 
and  for  this  reason  are  always  found  true. 
Hybrid  varieties  as  a  rule  were  formerly  con- 
fused with  pure  varieties,  and  in  many  in- 
stances our  knowledge  as  to  their  origin  is  quite 
insufficient  for  sharp  distinctions.  To  every 
student  of  nature  it  is  obvious,  that  crossing 
and  pure  variability  are  wholly  distinct  groups 
of  phenomena,  which  should  never  be  treated 
under  the  same  head,  or  under  the  same  name. 
Leaving  aside  polymorphy,  we  may  now  dis- 
cuss those  cases  of  variability,  in  which  the 
changes  themselves,  and  not  only  their  final 
results  play  a  part.  Of  such  changes  two  types 
exist.  First,  the  ever-recurring  variability, 
never  absent  in  any  large  group  of  individuals, 
and  determining  the  differences  which  are  al- 
ways to  be  seen  between  parents  and  their 
children,  or  between  the  children  themselves. 
This  type  is  commonly  called  '^  individual 
variabilitv  "  and  since  this  term  also  has  still 
other  meanings,  it  has  of  late  become  customary 
to   use   instead    the   term    ^'  fluctuating   varia- 


False  Atavism  191 

bility. ' '  And  to  avoid  the  repetition  of  the  lat- 
ter word  it  is  called  "  fluctuation.^'  In  con- 
trast to  these  fluctuations  are  the  so-called 
sports  or  single  varieties,  not  rarely  denomi- 
nated spontaneous  variations,  and  for  which  I 
propose  to  use  the  term  *^  mutations. '^  They 
are  of  very  rare  occurrence  and  are  to  be  con- 
sidered as  sudden  and  definite  steps. 

Lastly,  we  have  to  consider  those  varieties, 
which  vary  in  a  much  wider  range  than  the 
ordinary  ones,  and  seem  to  fluctuate  between 
two  opposite  extremes,  as  for  instance  varie- 
gated leaves,  cultivated  varieties  with  va- 
riegated or  striped  flowers,  double  flowers 
and  some  other  anomalies.  They  are  ever- 
sporting  and  ever-returning  from  one  type  to 
the  other.  If  however,  we  take  the  group  of 
these  extremes  and  their  intermediates  as  a 
whole,  this  group  remains  constant  during  the 
succeeding  generations.  Here  we  find  once 
more  an  instance  of  the  seemingly  contradictory 
combination  of  high  variability  and  absolute 
constancy.  It  means  that  the  range  of  varia- 
bility has  quite  definite  limits,  which  in  the  com- 
mon course  of  things,  are  never  transgressed. 

We  may  infer  therefore  that  the  word  varia- 
bility has  such  a  wide  range  of  meanings  that 
it  ought  never  be  used  without   explanation. 


192  Retrograde  Varieties 

Nothing  indeed,  is  more  variable  than  the  sig- 
nification of  the  term  variable  itself. 

For  this  reason,  we  will  furthermore  desig- 
nate all  variations  under  the  influence  of  neigh- 
bors with  the  new  and  special  term  ' '  vicinism. ' ' 
It  always  indicates  the  result  of  crossing. 

Leaving  this  somewhat  lengthy  terminolog- 
ical discussion,  we  now  come  to  the  description 
of  the  phenomenon  itself.  In  visiting  the  plan- 
tations of  the  seedsmen  in  summer  and  exam- 
ining the  large  fields  of  garden-flowers  from 
which  seed  is  to  be  gathered,  it  is  very  rare  to 
find  a  plot  quite  pure.  On  the  contrary,  occa- 
sional impurities  are  the  rule.  Every  plot 
shows  anomalous  individuals,  red  or  white 
flowers  among  a  field  of  blue,  normal  among 
laciniated,  single  among  double  and  so  on.  The 
most  curious  instance  is  atforded  by  dwarf 
varieties,  where  in  the  midst  of  hundreds  and 
thousands  of  small  individuals  of  the  same 
height,  some  specimens  show  twice  their  size. 
So  for  instance,  among  the  dwarfs  of  the  lark- 
spur. Delphinium  Ajacis. 

Everywhere  gardeners  are  occupied  in  de- 
stroying these  ''  atavists,"  as  they  call  them. 
When  in  full  bloom  the  plants  are  pulled  up 
and  thrown  aside.  Sometimes  the  degree  of 
impurity  is  so  high,  that  great  piles  of  dis- 
carded plants  of  the  same  species  lie  about  the 


False  Atavism  193 

paths,  as  I  have  seen  at  Erfurt  in  the  case  of 
numerous  varieties  of  the  Indian  cress  or  Tro- 
paeolum. 

Each  variety  is  purified  at  the  time  when  it 
shows  its  characters  most  clearly.  With  vege- 
tables, this  is  done  long  before  flowering,  but 
with  flowers  only  when  in  full  bloom,  and  with 
fruits,  usually  after  fertilization  has  been  ac- 
complished. It  needs  no  demonstration  to  show 
that  this  difference  in  method  must  result  in 
very  diverging  degrees  of  purity. 

We  will  confine  ourselves  to  a  consideration 
of  the  flowers,  and  ask  what  degree  of  purity 
may  be  expected  as  the  result  of  the  elimination 
of  the  anomalous  plants  during  the  period  of 
blooming. 

Now  it  is  evident  that  the  colors  and  forms 
of  the  flowers  can  only  be  clearly  distin- 
guished, when  they  are  fully  displayed.  Fur- 
thermore it  is  impossible  to  destroy  every 
single  aberrant  specimen  as  soon  as  it  is  seen. 
On  the  contrary,  the  gardener  must  wait  until 
all  or  nearly  all  the  individuals  of  the  same  va- 
riety have  displayed  their  characters,  as 
only  in  this  way  can  all  diverging  specimens 
be  eliminated  by  a  single  inspection.  Un- 
fortunately the  insects  do  not  wait  for  this 
selection.  They  fertilize  the  flowers  from  the 
beginning,  and  the  damage  will  have  been  done 


194  Retrograde  Varieties 

long  before  the  day  of  inspection  comes  around. 
Crosses  are  unavoidable  and  hybrid  seeds  will 
unavoidably  come  into  the  harvest.  Their 
number  may  be  limited  by  an  early  eradication 
of  the  vicinists,  or  by  the  elimination  of  the 
first  ripe  seeds  before  the  beginning  of  the  regu- 
lar harvest,  or  by  other  devices.  But  some 
degree  of  impurity  will  remain  under  ordinary 
circumstances. 

It  seems  quite  superfluous  to  give  more  de- 
tails. In  any  case  in  which  the  selection  is  not 
done  before  the  blooming  period,  some  impuri- 
ties must  result.  Even  if  it  is  done  before  that 
time,  errors  may  occur,  and  among  hundreds 
and  thousands  of  individuals  a  single  anomalous 
one  may  escape  observation. 

The  conclusion  is,  that  flower  seeds  as  they 
are  offered  in  commerce,  are  seldom  found 
absolutely  pure.  Every  gardener  knows  that 
he  will  have  to  weed  out  aberrant  plants  in 
order  to  be  sure  of  the  purity  of  his  beds.  I 
tested  a  large  number  of  samples  of  seeds  for 
purity,  bought  directly  from  the  best  seed- 
growers.  Most  of  them  were  found  to  contain 
admixtures  and  wholly  pure  samples  were  very 
rare. 

I  will  now  give  some  illustrative  examples. 
From  seeds  of  a  yellow  snapdragon,  I  got  one 
red-flowered  specimen  among  half  a  hundred 


False  Atavism  195 

yellow  ones,  and  from  the  variety  "  Delila  " 
of  the  same  species  two  red  ones,  a  single  white 
and  two  belonging  to  another  variety  called 
''  Firefly."  CalUopsis  tinctoria  has  three  va- 
rieties, the  ordinary  type,  a  brown-flowered 
one  and  one  with  tubular  rays.  Seeds  of  each 
of  these  three  sorts  ordinarily  contain  a  few 
belonging  to  the  others.  Iberis  umbellata  rosea 
often  gives  some  white  and  violet  examples. 
The  '^  Swan  "  variety  of  the  opium-poppy,  a 
dwarfish  double-flowered  form  of  a  pure  white, 
contained  some  single-flowered  and  some  red- 
flowered  plants,  when  sown  from  cormnercial  seed 
are  said  to  be  pure.  But  these  were  only  occa- 
sional admixtures,  since  after  artificial  fertiliza- 
tion of  the  typical  specimens  the  strain  at  once 
became  absolutely  pure,  and  remained  so  for  a 
series  of  generations,  as  long  as  the  experiment 
was  continued.  Seeds  of  trees  often  contain 
large  quantities  of  impurities,  and  the  laciniated 
varieties  of  birch,  elder  and  walnut  have  often 
been  observed  to  come  true  only  in  a  small 
number  of  seedlings. 

In  the  case  of  new  or  young  varieties,  seed- 
merchants  often  warn  their  customers  as  to  the 
probable  degree  of  purity  of  the  seeds  offered, 
in  order  to  avoid  complaints.  For  example  the 
snow-white  variety  of  the  double  daisy,  BelUs 
perennis  plena,  was  offered  at  the  start  as  con- 


196  Retrograde  Varieties 

taining  as  much  as  20^  of  red-flowered  speci- 
mens. 

Many  fine  varieties  are  recorded  to  come  true 
from  seed,  as  in  the  case  of  the  holly  with 
yellow  fruits,  tested  by  Darwin.  Others  have 
been  found  untrue  to  a  relatively  high  degree, 
as  is  notorious  in  the  case  of  the  purple  beech. 
Seeds  of  the  laciniated  beech  gave  only  10^ 
of  laciniated  plants  in  experiments  made  by 
Strasburger;  seeds  of  the  monophyllous  aca- 
cia, Rohinia  Pseud-Acacia  monopJiylla,  were 
found  to  be  true  in  only  30^  of  the  seedlings. 
Weeping  ashes  often  revert  to  the  upright  type, 
red  May-thorns  (Crataegus)  sometimes  revert 
nearly  entirely  to  the  white  species  and  the 
yellow  cornel  berry  is  recorded  to  have  reverted 
in  the  same  way  to  the  red  berries  of  the  Cor- 
nus  Mas, 

Varieties  have  to  be  freed  by  selection  from 
all  such  impurities,  since  isolation  is  a  means 
which  is  quite  impracticable  under  ordinary 
circumstances.  Isolation  is  a  scientific  require- 
ment that  should  never  be  neglected  in  ex- 
periments, indeed  it  may  be  said  to  be  the  first 
and  most  important  requisite  for  all  exact  re- 
search in  questions  of  variability  and  inherit- 
ance. But  in  cultivating  large  fields  of  allied  va- 
rieties for  commercial  purposes,  it  is  impossible 
to  grow  them  at  such  distances  from  each  other 


False  Atavism  197 

as  to  prevent  cross-pollination  by  the  visits  of 
bees. 

This  purification  must  be  done  in  nearly  every 
generation.  The  oldest  varieties  are  to  be  sub- 
jected to  it  as  well  as  the  latest.  There  is  no 
regular  amelioration,  no  slow  progression  in  the 
direction  of  becoming  free  from  these  admix- 
tures. Continuous  selection  is  indispensable  to 
maintain  the  races  in  the  degree  of  purity  which 
is  required  in  commerce,  but  it  does  not  lead  to 
any  improvement.  Nor  does  it  go  so  far  as  to 
become  unnecessary  in  the  future.  This  shows 
that  there  must  be  a  continuous  source  of  im- 
purities, which  in  itself  is  not  neutralized  by 
selection,  but  of  which  selection  can  only  elim- 
inate the  deteriorating  elements. 

The  same  selection  is  usually  applied  to  new 
varieties,  when  they  occasionally  arise.  In  this 
case  it  is  called  '^  fixing,"  as  gardeners  gener- 
ally believe  that  through  selection  the  varieties 
are  brought  to  the  required  degree  of  purity. 
This  belief  seems  to  rest  mainly  on  obser- 
vations made  in  practice,  where,  as  we  have  seen, 
isolation  is  of  very  rare  application.  Most  va- 
rieties would  no  doubt  be  absolutely  pure  from 
the  first  moment  of  their  existence,  if  it  were 
only  possible  to  have  them  purely  fertilized. 
But  in  practice  this  is  seldom  to  be  obtained. 
Ordinarily  the  breeder  is  content  with  such  slow 


198  Retrograde  Varieties 

improvement  as  may  be  obtained  with  a  mini- 
mum of  cost,  and  this  mostly  implies  a  culture  in 
the  same  part  of  the  nursery  with  older  varie- 
ties of  the  same  species.  Three,  four  or  five 
years  are  required  to  purify  the  novelty,  and 
as  this  same  length  of  time  is  also  required  to 
produce  sufficient  quantities  of  seed  for 
commercial  purposes,  there  is  no  strong 
desire  to  shorten  the  period  of  selection  and 
fixation.  I  had  occasion  to  see  this  process  go- 
ing on  with  sundry  novelties  at  Erfurt  in 
Germany.  Among  them  a  chamois-colored  va- 
riety of  the  common  stock,  a  bluish  Clarkia 
elegans  and  a  curiously  colored  opium-poppy 
may  be  mentioned.  In  some  cases  the  cross- 
fertilization  is  so  overwhelming,  that  in  the 
next  generation  the  novelty  seems  entirely  to 
have  disappeared. 

The  examples  given  may  suffice  to  convey  a 
general  idea  of  the  phenomenon,  ordinarily 
called  atavism  by  gardeners,  and  considered 
mostly  to  be  the  effect  of  some  innate  tendency 
to  revert  to  the  ancestral  form.  It  is  on  this 
conception  that  the  almost  universal  belief 
rests,  that  varieties  are  distinguished,  as  such, 
from  species  by  their  inconstancy.  Now  I  do 
not  deny  the  phenomenon  itself.  The  impurity 
of  seeds  and  cultures  is  so  general  and  so  mani- 
fest, and  may  so  easily  be  tested  by  every  one 


False  Atavism  199 

that  it  cannot  reasonably  be  subjected  to  any 
doubt.  It  must  be  conceded  to  be  a  fact,  that 
varieties  as  a  rule  revert  to  their  species  under 
the  ordinary  circumstances  of  commercial  cul- 
ture. And  I  cannot  see  any  reason  why  this 
fact  should  not  be  considered  as  stating  a  prin- 
cipal difference  between  varieties  and  species, 
since  true  species  never  sport  into  one  another. 

My  objection  only  refers  to  the  explanation 
of  the  observed  facts.  According  to  my  view 
nearly  all  these  ordinary  reversions  are  due  to 
crosses,  and  it  is  for  this  reason  that  I  proposed 
to  call  them  by  a  separate  name,  that  of  *  *  vicin- 
ists."  Varieties  then,  by  means  of  such  spon- 
taneous intercrossing  sport  into  one  another, 
while  species  either  do  not  cross,  or  when  cross- 
ing produce  hybrids  that  are  otherwise  consti- 
tuted and  do  not  give  the  impression  of  atavis- 
tic reversion. 

I  must  not  be  content  with  proposing  this 
new  conception,  but  must  give  the  facts  on 
which  this  assumption  rests.  These  facts  are 
the  results  of  simple  experiments,  which  never- 
theless are  by  no  means  easy  to  carry  out,  as 
they  require  the  utmost  care  to  secure  the 
absolute  purity  of  the  seeds  that  are  employed. 
This  can  only  be  guaranteed  by  previous  cul- 
tures of  isolated  plants  or  groups  of  plants,  or 
by  artificial  pollination. 


200  Retrograde  Varieties 

Once  sure  of  this  preliminary  condition,  the 
experiment  simply  consists  in  growing  a  variety 
at  a  given  distance  from  its  species  and  allow- 
ing the  insects  to  transfer  the  pollen.  After 
harvesting  the  seed  thus  subjected  to  the  pre- 
sumed cause  of  the  impurities,  it  must  be 
sown  in  quantities,  large  enough  to  bring  to 
light  any  slight  anomaly,  and  to  be  examined 
during  the  period  of  blooming. 

The  wild  seashore  aster,  Aster  Tripolium, 
will  serve  as  an  example.  It  has  pale  violet  or 
bluish  rays,  but  has  given  rise  to  a  white  va- 
riety, which  on  testing,  I  have  found  pure  from 
seed.  Four  specimens  of  this  white  variety 
were  cultivated  at  a  distance  of  nearly  100 
meters  from  a  large  lot  of  plants  of  the  bluish 
species.  I  left  fertilization  to  the  bees,  har- 
vested the  seeds  of  the  four  whites  separately 
and  had  from  them  the  following  year  more  than 
a  thousand  flowering  plants.  All  of  them  were 
of  the  purest  white,  with  only  one  exception, 
which  was  a  plant  with  the  bluish  rays  of  the 
species,  wholly  reverting  to  its  general  type.  As 
the  variety  does  not  give  such  reversions  when 
cultivated  in  isolation,  this  sport  was  obviously 
due  to  some  cross  in  the  former  year.  In  the 
same  way  I  tried  the  white  Jacob's  ladder, 
Polemonium  coeruleum  album  in  the  neighbor- 
hood of  the  blue-flowered  species,  the  distance 


False  Atavism  201 

in  this  case  being  only  40  meters.  Of  two  hun- 
dred seeds  one  became  a  blue  atavist,  or  rather 
vicinist,  while  all  others  remained  true  to  the 
white  type.  The  same  was  observed  in  the 
white  creeping  thyme,  or  Thymus  Serpyllum 
album,  and  the  white  self-heal,  Brunella  vul- 
garis alba,  gave  even  so  much  as  28^  seed- 
lings with  purple  corollas  out  of  some  400 
specimens,  after  being  cultivated  in  close  prox- 
imity to  its  parent-species.  I  have  tried  many 
other  species,  but  always  with  the  same  result. 
Such  atavists  only  arise  by  cultivation  in  the 
proximity  of  allied  varieties,  never  in  isolation. 
They  are  not  real  atavists,  but  only  vicinists. 

In  order  to  show  this  yet  more  clearly,  I 
made  another  experiment  with  the  white  self- 
heal.  I  had  a  lot  of  the  pinnate-leaved  variety 
with  purple  flowers  and  somewhat  stouter 
stems,  and  cultivated  single  plants  of  the  white- 
flowering  sort  at  distances  that  varied  from 
2-16  meters.  The  seeds  of  each  plant  were 
collected  and  sown  separately,  those  of  the 
nearest  gave  up  to  5  or  6  hybrids  from  the  seeds 
of  one  parent,  while  those  of  the  farthest  gave 
only  one  purple-flowered  plant  for  each  parent. 
Evidently  the  chance  of  the  pollen  being  carried 
by  bees  is  much  greater  on  short  than  on  longer 
distances. 

True  hybrids  between  species  may  arise  in 


202  Retrograde  Varieties 

quite  the  same  way,  and  since  it  is  obviously 
impossible  to  attribute  them  to  an  innate  ten- 
dency to  reversion,  they  afford  an  absolutely 
irrefutable  proof  of  the  assertion  that  pollen 
is  often  brought  by  insects  from  one  lot  of 
plants  to  another.  In  this  way  I  obtained  a 
hybrid  between  the  common  Jacob's  ladder  and 
the  allied  species  Polemonium  dissectum.  With 
a  distance  of  100  meters  between  them  I  had 
two  hybrid  seeds  among  a  hundred  of  pure 
ones.  At  a  similar  distance  pollen  was  carried 
over  from  the  wild  radish,  Raphanus  Raphanis- 
trum,  to  the  allied  Raphanus  caudatus,  and  I 
observed  the  following  year  some  very  nice  hy- 
brids among  my  seedlings.  A  hybrid-bean  be- 
tween Phaseolus  nanus  and  P.  multiflorus,  and 
some  hybrids  between  the  yellow  daisy, 
Chrysanthemum  segetum  and  the  allied  Chrys- 
anthemum coronarium  or  ox-eye  daisy  which 
also  arose  spontaneously  in  my  garden  between 
parents  cultivated  at  recorded  distances,  might 
further  be  noted.  Further  details  of  these  ex- 
periments need  not  be  given.  Suffice  to  say, 
that  occasional  crosses  between  species  do 
occur,  and  not  even  rarely,  that  they  are  easily 
recognized  as  such  and  cannot  be  confused  with 
cases  of  atavism,  and  that  therefore  they  give 
proof  to  the  assumption  that  in  the  same  way 
crosses  ordinarily  occur  also  between  varieties 


False  Atavism  203 

of  the  same  species,  if  cultivated  at  small  dis- 
tances apart,  say  40  -  50  meters  or  even  more. 

Vicinism  therefore,  may  play  a  part  in  all 
such  cultures,  enough  to  account  for  all  the 
impurities  observed  in  the  nurseries  or  in  com- 
mercial seed-samples. 

Of  course  this  whole  discussion  is  limited  to 
such  species  as  are  not  only  as  a  rule  visited  by 
insects,  but  are  dependent  on  these  visits  for 
their  fertilization.  Most  of  our  garden-flowers 
are  included  in  this  category.  If  not  then  we 
may  expect  to  find  the  cultures  and  seeds  pure, 
irrespective  of  the  distances  between  allied  va- 
rieties, as  for  instance  with  peas,  which  are 
known  to  be  self-fertilizing.  Another  instance 
is  given  by  the  barley.  One  of  the  most  curious 
anomalous  varieties  of  this  cereal,  is  the 
^^  Nepaul-barley, "  with  its  small  adventitious 
flowers  on  the  palets  or  inner  scales.  It  is  a 
very  old,  widely  cultivated  sort,  which  always 
comes  true  from  seed,  and  which  has  been 
tested  in  repeated  experiments  in  my  garden. 
The  spikelets  of  this  curious  plant  are  one- 
flowered  and  provided  with  two  linear  glumes 
or  outer  scales.  Of  the  inner  scales  or  palets, 
the  outer  one  is  three-lobed  at  the  summit,  hence 
the  varietal  name  of  Hordeum  vulgare  trifur- 
catum.  The  central  lobe  is  oblong  and  hollow, 
covering  a  small  supernumerary  floret  inserted 


204  Retrograde  Varieties 

at  its  base.  The  two  lateral  lobes  are  narrower, 
sometimes  linear,  and  are  often  prolonged  into 
an  awn,  which  is  generally  turned  away  from 
the  center  of  the  spike.  The  central  lobe  some- 
times bears  two  florets  at  its  base,  although  but 
one  is  usually  present  and  it  may  be  incomplete. 
I  might  give  one  more  instance  from  my  own 
experience.  A  variety  of  the  evening -primrose 
with  small  linear  petals  was  once  found  by  one 
of  my  sons  growing  wild  near  Amsterdam.  It 
was  represented  by  only  one  individual,  flower- 
ing among  a  great  many  of  the  ordinary  type 
with  broad  petals.  But  the  evening-primroses 
open  their  anthers  in  the  morning,  fertilize 
themselves  during  the  day,  and  only  display 
their  beautiful  flowers  in  the  evening,  after  the 
pollination  has  been  accomplished.  They  then 
allure  evening  moths,  such  as  Agrotis  and 
Plusia,  by  their  bright  color,  their  sweet  honey- 
smell  and  their  nectar.  Since  the  fertiliza- 
tion is  accomplished  many  hours  before  opening, 
crosses  are  effected  only  in  rare  instances,  and 
the  seeds  commonly  remain  true  to  the  parent- 
type.  The  seeds  of  this  one  plant,  when  sown 
separately  in  my  garden,  produced  exclusively 
flowers  with  the  small  linear  petals  of  their 
parent.  Although  I  had  a  hundred  individuals 
bearing  many  thousands  of  flowers,  there  was 
not  an  instance  of  reversion.     And  such  would 


False  Atavism  205 

immediately  have  been  observed,  had  it  oc- 
curred, because  the  hybrids  between  the  cruci- 
ate and  the  normal  flowers  are  not  intermediate, 
but  bear  the  broad  petals  of  the  0.  biennis. 

We  may  now  take  up  another  phase  of  the 
question,  that  of  the  running  out  of  new  varie- 
ties, shortly  after  their  introduction  into  a  new 
country,  or  later. 

The  most  widely  known  instance  of  this  is 
that  of  the  American  corn  in  Baden,  recorded 
by  Metzger  and  quoted  by  Darwin  as  a  remark- 
able instance  of  the  direct  and  prompt  action 
of  climate  on  a  plant.  It  has  since  been  con- 
sidered as  a  reversion  to  the  old  type.  Such 
reversions  invariably  occur,  according  to  Wal- 
lace, in  cases  of  new  varieties,  which  have 
been  produced  quickly.  But  as  we  now  know, 
such  reversions  are  due  to  spontaneous  crosses 
with  the  old  form,  and  to  the  rule,  that  the 
hybrids  of  such  origin  are  not  intermediate, 
but  assume  the  features  of  the  older  of  the 
two  parents.  In  the  light  of  this  experience, 
Metzger 's  observation  becomes  a  typical  in- 
stance of  vicinism.  It  relates  to  the  ^*  Tusca- 
rora  "  corn  of  St.  Louis,  a  variety  with  broad 
and  flat  white  seeds. 

About  the  year  1840,  this  corn  was  introduced 
into  Baden  in  Germany,  and  cultivated  by  Metz- 
ger.    In  the  first  year  it  came  true  to  type,  and 


206  Retrograde  Varieties 

attained  a  height  of  12  feet,  but  the  season  did 
not  allow  its  seeds  to  ripen  normally.  Only 
a  few  kernels  were  developed  before  the  winter. 
From  this  seed  plants  of  a  wholly  different 
type  came  the  next  year,  of  smaller  stature,  and 
with  more  brownish  and  rounded  kernels.  Thev 
also  flowered  earlier  and  ripened  a  large  num- 
ber of  seeds.  The  depression  on  the  outer  side 
of  the  seed  had  almost  disappeared,  and  the 
original  white  had  become  darker.  Some  of  the 
seeds  had  even  become  yellow  and  in  their 
rounded  form  they  approached  the  common 
European  maize.  Obviously  they  were  hybrids, 
assuming  the  character  of  their  pollen-parent, 
which  evidently  was  the  ordinary  corn,  culti- 
vated all  around.  The  observation  of  the  next 
year  showed  this  clearly,  for  in  the  third  gener- 
ation nearly  all  resemblance  to  the  original  and 
very  distinct  American  species  was  lost.  If 
we  assume  that  only  those  seeds  ripened  which 
reverted  to  the  early-ripening  European  type, 
and  that  those  that  remained  true  to  the  very 
late  American  variety  could  not  reach  maturity, 
the  case  seems  to  be  wholly  comprehensible, 
without  supposing  any  other  factors  to  have 
been  at  work  than  those  of  vicinism,  which 
though  unknown  at  the  period  of  Metzger  ^s  and 
Darwin's  writings,  seems  now  to  be  fully  un- 
derstood.    No  innate  tendency  to  run  out  and 


False  Atavism  207 

no  changing  influence  of  the  climate  are  re- 
quired for  an  adequate  explanation  of  the 
facts. 

In  the  observation  quoted,  what  astonishes  us 
most,  is  the  great  rapidity  of  the  change,  and  the 
short  time  necessary  for  the  offspring  of  the 
accidental  crosses  to  completely  supplant  the  in- 
troduced type.  In  the  lecture  on  the  selection 
of  elementary  species,  closely  analogous  cases 
were  described.  One  of  them  was  the  wild  oat 
or  Avena  fatua  which  rapidly  supplants  the 
cultivated  oats  in  bad  years  in  parts  of  the 
fields.  Other  instances  were  the  experiments  of 
Risler  with  the  ^'  Galland  "  wheat  and  the  ob- 
servation of  Rimpau  on  '^  Rivett's  bearded  " 
wheat. 

Before  leaving  the  question  of  vicinism  and 
its  bearing  on  the  general  belief  of  the  insta- 
bility of  varieties,  which  when  tested  with  due 
care,  prove  to  be  quite  stable,  it  may  be 
as  well  to  consider  the  phenomena  from 
another  point  of  view.  Our  present  knowledge 
of  the  effects  of  crosses  between  varieties  ena- 
bles us  to  formulate  some  general  rules,  which 
may  be  used  to  calculate,  and  in  some  way  to 
predict,  the  nature  of  the  impurities  which  nec- 
essarily attend  the  cultivation  of  allied  species 
in  close  vicinity.  And  this  mode  of  cultivation 
being  in  almost  universal  use  in  the  larger  niu'- 


208  Retrograde  Varieties 

series,  we  may,  by  this  discussion,  arrive  at  a 
more  scientific  estimation  of  the  phenomena  of 
vicinism,  hitherto  described. 

The  simplest  case  that  may  be  given,  is  when 
an  ordinary  retrograde  variety  is  cultivated 
with  the  species  to  which  it  belongs.  For  in- 
stance, if  dwarfs  are  cultivated  next  to  the  taller 
type,  or  a  white  variety  next  to  the  red  or 
blue-flowering  species,  or  thornless  fonns  in 
neighboring  beds  with  the  armed  species. 
Bees  and  humble-bees,  butterflies  and  moths  are 
seen  flying  from  flower  to  flower,  collecting  the 
honey  and  carrying  pollen.  I  frequently  saw 
them  cross  the  limits  of  the  neighboring  beds. 
Loaded  with  the  pollen  of  the  variety  they  visit 
the  flowers  of  the  different  species  and  impreg- 
nate the  stigma  with  it.  And  returning  to  the 
variety  they  bring  about  similar  crosses  in  the 
flowers  of  the  latter.  Hybrid  seeds  will  devel- 
op in  both  cases  and  become  mixed  with  the 
crop.  We  now  have  to  ask  the  question,  what 
sort  of  plants  will  arise  from  these  hybrid 
seeds.  As  a  general  rule  we  may  state,  first, 
that  the  hybrids  of  either  form  of  cross  are 
practically  the  same,  secondly  that  they  are  not 
intermediate,  but  that  the  character  of  one  par- 
ent prevails  to  the  almost  absolute  exclusion 
of  the  other  and  in  the  third  place  that  the  older 
character  dominates  the  younger. 


False  Atavism  209 

The  hybrid  offspring  will  therefore,  in  the 
main,  have  the  character  of  the  species  and  be 
indistinguishable  from  it,  or  show  only  such 
differences  as  escape  ordinary  observation. 
When  occurring  in  the  seeds  of  the  variety 
they  betray  themselves  as  soon  as  the  dif- 
ferential characters  are  displayed.  Between 
the  thousands  of  flowering  plants  of  a  white 
variety  the  hybrids  will  instantly  catch  the  eye 
by  their  red  or  blue  corollas.  Quite  the  con- 
trary effect  results  from  the  admixture  of  hy- 
brids with  the  seeds  of  the  species  itself.  Here 
no  difference  will  show  itself,  even  in  the  full- 
est bloom.  The  effect  of  the  spontaneous 
crosses  will  pass  unobserved.  The  strain,  if 
pure  in  the  first  year,  will  seem  to  be  still  in  the 
same  condition.  Or  in  other  terms,  the  una- 
voidable spontaneous  crosses  will  disturb  the 
purity  of  the  variety  in  the  second  year,  while 
they  do  not  seem  to  interfere  at  all  with  the  uni- 
formity of  the  species.  The  direct  effect  of  the 
visits  of  the  insects  is  evident  in  the  first  case, 
but  passes  unobserved  in  the  latter. 

From  this  it  would  seem,  that  spontaneous 
crosses  are  hurtful  to  varieties,  but  are  in- 
nocuous to  true  species.  Certainly  this  would 
be  so,  were  there  no  selection.  But  it  is  easily 
seen,  that  through  this  operation  the  effect  be- 
comes quite  the  opposite.     For  when  the  fields 


210  Retrograde  Varieties 

are  inspected  at  the  time  of  the  fullest  display 
of  the  varietal  characters,  the  obvious  hybrids 
will  be  eliminated,  but  the  hidden  ones  will  of  ne- 
cessity be  spared,  as  they  are  concealed  among 
the  species  by  the  similarity  of  their  type. 
Hence,  the  harvest  of  the  variety  may  be  ren- 
dered pure  or  nearly  so,  while  the  harvest  of 
the  species  will  retain  the  seeds  of  the  hybrids. 
Moreover  it  will  contain  seeds  originated  by  the 
spontaneous  but  numerous  crosses  of  the  true 
plants  with  the  sparsely  intermingled  hybrids. 

This  brings  us  to  the  question,  as  to  what  will 
be  the  visible  consequences  of  the  occurrence  of 
such  invisible  hybrids  in  the  following  gener- 
ation. In  opposition  to  the  direct  effects  just 
described,  we  may  call  them  indirect.  To  judge 
of  their  influence,  we  must  know  how  hybrid 
seeds  of  the  first  generation  behave. 

In  one  of  our  lectures  we  will  deal  with  the 
laws  that  show  the  numerical  relations  known 
as  the  laws  of  Mendel.  But  for  our  present 
purpose,  these  numerical  relations  are  only  of 
subordinate  importance.  What  interests  us  here 
is  the  fact  that  hybrids  of  varieties  do  not  re- 
main constant  in  the  second  generation  but  usu- 
ally split  as  it  is  said,  remaining  hybrid 
only  in  part  of  their  offspring,  the  other  por- 
tion returning  to  the  parental  types.  This  how- 
ever, will  show  itself  only  in  those  individuals 


False  Atavism  211 

which  reassume  the  character  of  the  varietal 
parent,  all  the  others  apparently  remaining  true 
to  the  type  of  the  species.  Now  it  is  easy  to 
foresee  what  must  happen  in  the  second  gen- 
eration if  the  first  generation  after  the  cross 
is  supposed  to  be  kept  free  from  new  vicinistic 
influences,  or  from  crosses  with  neighboring 
varieties. 

We  may  limit  ourselves  in  the  first  place  to 
the  seeds  of  the  unobserved  hybrids.  For  the 
greater  part  they  will  repeat  the  character  of 
their  parents  and  still  remain  concealed.  But  a 
small  number  will  display  the  varietal  marks, 
as  for  example  showing  white  flowers  in  a 
field  of  blue  ones.  Hence,  the  indirect  conse- 
quence of  the  spontaneous  crosses  will  be  the 
same  in  the  species,  as  was  the  direct  effect 
in  the  variety,  only,  that  it  appears  a  year  later. 
It  will  then  be  eliminated  in  the  process  of 
selection. 

Obviously,  this  elimination  conduces  only  to 
a  partial  purification.  The  conspicuous  plants 
will  be  destroyed,  but  a  greater  number  of  hy- 
brids will  remain,  still  concealed  by  their  re- 
semblance to  the  general  type  and  will  be 
spared  to  repeat  the  same  process  next  year. 
So  while  the  variety  may  be  freed  every  year 
from  the  impurities  brought  into  it  in  the  pre- 
ceeding  summer,  the  admixtures   of  the   spe- 


212  Retrograde  Varieties 

cies  will  continue  during  a  number  of  years, 
and  it  may  not  be  possible  to  get  rid  of  them 
at  all. 

It  is  an  often  recurring  assertion  that  white 
varieties  of  colored  species  are  the  most  stable 
of  all  horticultural  races.  They  are  often  said 
to  be  at  least  as  constant  as  the  species  itself, 
and  even  to  surpass  it  in  this  quality.  With  our 
present  state  of  knowledge,  the  explanation  of 
this  general  experience  is  easily  given.  For  se- 
lection removes  the  effect  of  spontaneous  cross- 
es from  the  variety  in  each  year,  and  renders  it 
practically  pure,  while  it  is  wholly  inadequate 
to  produce  the  same  effects  on  the  species,  be- 
cause of  the  concealed  hybrids. 

The  explanation  given  in  this  simple  instance 
may  be  applied  to  the  case  of  different  varieties 
of  the  same  species,  when  growing  together 
and  crossed  naturally  by  insects. 

It  would  take  too  long  to  go  into  all  the  de- 
tails that  present  themselves  here  to  the  stu- 
dent of  nature  and  of  gardens.  I  will 
only  state,  that  since  varieties  differ  princi- 
pally from  their  species  by  the  lack  of  some 
sharp  character,  one  variety  may  be  character- 
ized by  the  lack  of  color  of  the  flowers,  another 
by  the  lack  of  pubescence,  a  third  by  being 
dwarfed,  and  so  on.  Every  character  must  be 
studied  separately  in  its  effects  on  the  offspring 


False  Atavism  213 

of  the  crosses.  And  it  is  therefore  easily  seen, 
that  the  hybrids  of  two  varieties  may  resemble 
neither  of  them,  but  revert  to  the  species  itself. 
This  is  necessarily  and  commonly  the  case, 
since  it  is  always  the  older  or  positive  charac- 
ters that  prevail  in  the  hybrids  and  the 
younger  or  negative  that  lie  hidden.  So  for  in- 
stance, a  blue  dwarf  larkspur,  crossed  with  a 
tall  white  variety,  must  give  a  tall  blue  hybrid, 
reassuming  in  both  characters  the  essentials 
of  the  species. 

Keeping  this  rule  in  view,  it  will  be  easy  to 
calculate  what  may  be  expected  from  sponta- 
neous crosses  for  a  wide  range  of  occurrences, 
and  thus  to  find  an  explanation  of  innumerable 
cases  of  apparent  variability  and  reversion  in 
the  principle  of  vicinism.  Students  have  only 
to  recollect  that  specific  characters  prevail  over 
varietal  ones,  and  that  every  character  com- 
petes only  with  its  own  antagonist.  Or  to  give 
a  sharper  distinction :  whiteness  of  flowers  can- 
not be  expected  to  be  interchanged  with 
pubescence  of  leaves. 

In  concluding  I  will  point  out  another  danger 
which  in  the  principle  of  vicinism  may  be 
avoided.  If  you  see  a  plant  in  a  garden  with  all 
the  characteristics  of  its  species,  how  can  you 
be  sure  that  it  is  truly  a  representative  of  the 
species,    and   not   a   hybrid!     The   prevailing 


214  Retrograde  Varieties 

characters  are  in  either  case  the  same.  Perhaps 
on  close  inspection  you  may  find  in  some  cases 
a  slight  difference,  some  character  being  not 
as  fully  developed  in  the  hybrid  as  in  the  spe- 
cies. But  when  such  is  not  the  case,  or  where 
the  opportunity  for  such  a  closer  examination 
is  wanting,  a  hybrid  may  easily  be  taken  for  a 
specimen  of  the  pure  race.  Now  take  the  seeds 
of  your  plant  and  sow  them.  If  you  had  not 
supposed  it  to  be  hybrid  you  will  be  astonished 
at  finding  among  its  progeny  some  of  a  wholly 
different  type.  You  will  be  led  to  conclude 
that  you  are  observing  a  sudden  change  in 
structure  such  as  is  usually  called  a  sport. 

Or  in  other  words  you  may  think  that  you  are 
assisting  at  the  origination  of  a  new  variety. 
If  you  are  familiar  with  the  principle  of  vicin- 
ism,  you  will  refrain  from  such  an  inference  and 
consider  the  supposition  of  a  hybrid  origin. 
But  in  former  times,  when  this  principle 
was  still  unknown  and  not  even  guessed 
at,  it  is  evident  that  many  mistakes  must  have 
been  made,  and  that  many  an  instance,  which 
until  now  has  been  considered  reliable  proof 
of  a  so-called  single  variation,  is  in  fact  only  a 
case  of  vicinism.  In  reading  the  sparse  litera- 
ture on  sports,  numerous  cases  will  be  found, 
which  cannot  stand  this  test.  In  many  instances 
crossing  must  be  looked  to  as  an  explanation, 


False  Atavism  215 

and  in  other  cases  the  evidence  relied  upon  does 
not  suffice  to  exclude  this  assumption.  Many 
an  old  argument  has  of  late  lost  its  force  by 
this  test. 

Returning  to  our  starting  point  we  may  now 
state  that  regular  reversions  to  a  specific  type 
characterize  a  form  as  a  variety  of  that  species. 
These  reversions,  however,  are  not  due  to  an 
innate  tendency,  but  to  unobserved  spontaneous 
crosses. 


Lecture  VIII 


LATENT    CHAEACTERS 


No  organism  exhibits  all  of  its  qualities  at 
any  one  time.  Many  of  them  are  generally 
dormant  and  await  a  period  of  activity.  For 
some  of  them  this  period  comes  regularly,  while 
in  others  the  awakening  depends  upon  external 
influences,  and  consequently  occurs  very  irreg- 
ularly. Those  of  the  first  group  correspond  to 
the  differences  in  age ;  the  second  constitute  the 
responses  of  the  plant  to  stimuli  including 
wound-injuries. 

Some  illustrative  examples  may  be  quoted  in 
order  to  give  a  precise  idea  of  this  general  con- 
ception of  dormant  or  latent  characters.  Seed- 
leaves  are  only  developed  in  the  seed  and  the 
seedling;  afterwards,  during  the  entire  life- 
time of  the  plant,  the  faculty  of  producing  them 
is  not  made  use  of.  Every  new  generation  of 
seeds  however,  bears  the  same  kind  of  seed- 
leaves,  and  hence  it  is  manifest  that  it  is 
the  same  quality,  which  shows  itself  from  time 
to  time. 

216 


Latent  Characters  217 

The  primary  leaves,  following  the  seed-leaves, 
are  different  in  many  species  from  the  later 
ones,  and  the  difference  is  extremely  pro- 
nounced in  some  cases  of  reduction.  Often, 
when  leaves  are  lacking  in  the  adult  plant,  be- 
ing replaced  by  flattened  stalks  as  in  the  case 
of  the  acacias,  or  by  thorns,  or  green  stems  and 
twigs  as  in  the  prickly  broom  or  JJlex  europaeus, 
the  first  leaves  of  the  young  plant  may  be  more 
highly  differentiated,  being  pinnate  in  the  first 
case  and  bearing  three  leaflets  in  the  second  in- 
stance. This  curious  behavior  which  is  very 
common,  brings  the  plants,  when  young,  nearer 
to  their  allies  than  in  the  adult  state,  and  mani- 
festly implies  that  the  more  perfect  state  of 
the  leaves  is  latent  throughout  the  life  of  the 
plant,  with  the  exception  of  the  early  juvenile 
period. 

Eucalyptus  Globulus,  the  Australian  gum- 
tree,  has  opposite  and  broadly  sessile  leaves 
during  the  first  years  of  its  life.  Later  these 
disappear  and  are  replaced  by  long  sickle- 
shaped  foliage  organs,  which  seem  to  be  scat- 
tered irregularly  along  the  branches.  The  juve- 
nile characters  manifestly  lie  dormant  during 
the  adult  period,  and  that  this  is  so,  may  be 
shown  artificially  by  cutting  off  the  whole  crown 
of  the  tree,  when  the  stem  responds  by  produc- 
ing numerous  new  branches,  which  assume  the 


218  Retrograde  Varieties 

shape  proper  to  the  young  trees,  bearing  sessile 
and  opposite  leaves. 

It  seems  quite  unnecessary  to  give  further 
instances.  They  are  familiar  to  every  student. 
It  is  almost  safe  to  say  that  every  character  has 
its  periods  of  activity  and  of  inactivity,  and 
numbers  of  flowers  and  fruits  can  be  mentioned 
as  illustrations.  One  fact  may  be  added  to 
show  that  nearly  every  part  of  the  plant  must 
have  the  power  of  producing  all  or  nearly  all 
the  characters  of  the  individual  to  which  it 
belongs.  This  proof  is  given  by  the  formation 
of  adventitious  buds.  These,  when  once 
formed,  may  grow  out  into  twigs,  with  leaves 
and  flowers  and  roots.  They  may  even  be  sep- 
arated from  the  plants  and  used  as  cuttings 
to  reproduce  the  whole.  Hence  we  may 
conclude  that  all  tissues,  which  possess  the 
power  of  producing  adventitious  buds,  must 
conceal  in  a  latent  state,  all  the  numerous  char- 
acters required  for  the  full  development  of  the 
whole  individual. 

Adventitious  buds  may  proceed  from  spe- 
cialized cells,  as  on  the  margin  of  the  leaves  of 
Bryopliyllum  calycinum;  or  from  the  cells  of 
special  tissues,  as  in  the  epidermis  of  the  be- 
gonias; or  they  may  be  provoked  by  wounds 
in  nearly  every  part  of  the  plant,  provided  it 
be  able  to  heal  the  wound  by  swelling  tissues  or 


Latent  Characters  219 

callus.  The  best  instance  is  afforded  by  elms 
and  by  the  horse-chestnut.  If  the  whole  tree  is 
hewn  down  the  trunk  tries  to  repair  the  injury 
by  producing  small  granulations  of  tissue  be- 
tween the  wood  and  the  bark,  which  gradually 
coalesce  while  becoming  larger.  From  this  new 
ring  of  living  matter  innumerable  buds  arise, 
that  expand  into  leafy  branches,  showing 
clearly  that  the  old  trunk  possesses,  in  a  latent 
state,  all  the  qualities  of  the  whole  crown.  In- 
deed, such  injured  stumps  may  be  used  for  the 
production  of  copses  and  hedges. 

All  the  hitherto  recorded  cases  of  latency 
have  this  in  common,  that  they  may  become  ac- 
tive during  the  life-time  of  any  given  individual 
once,  or  oftener.  This  may  be  called  the  ordi- 
nary type  of  latency. 

Besides  this  there  is  another  form  of  latent 
characters,  in  which  this  awakening  power  is 
extremely  limited,  or  wholly  absent.  It  is  the 
systematic  latency,  which  may  be  said  to  be- 
long to  species  and  varieties  in  the  same  way  as 
the  ordinary  latency  belongs  to  individuals. 
As  this  individual  latency  may  show  itself  from 
time  to  time  during  the  life  of  a  given  plant,  the 
first  may  only  become  active  from  time  to  time 
during  the  whole  existence  of  the  variety  or  the 
species.  It  has  no  regular  period  of  activity, 
nor  may  it  be  incited  by  artificial  stimulation. 


220  Retrograde  Varieties 

It  emerges  from  concealment  only  very  rarely 
and  only  on  its  own  initiative.  Such  instances 
of  atavism  have  been  described  in  previous  lec- 
tures, and  their  existence  has  been  proved  be- 
yond doubt. 

Systematic  latency  explains  the  innumerable 
instances  in  which  species  are  seen  to  lack  def- 
inite characteristics  which  ordinarily  do  not 
fail,  either  in  plants  at  large,  or  in  the  group 
or  family  to  which  the  plant  belongs.  If  we 
take  for  instance  the  broom-rape  or  Orobanche, 
or  some  other  pale  parasite,  we  explain  their 
occurrence  in  families  of  plants  with  green 
leaves,  by  the  loss  of  the  leaves  and  of  the  green 
color.  But  evidently  this  loss  is  not  a  true  one, 
but  only  the  latency  of  those  characters. 
And  even  this  latency  is  not  a  complete  one,  as 
little  scales  remind  us  of  the  leaves,  and  traces 
of  chlorophyll  still  exist  in  the  tissues.  Nu- 
merous other  cases  will  present  themselves  to 
every  practical  botanist. 

Taking  for  granted  that  characters,  having 
once  been  acquired,  may  become  latent,  and  that 
this  process  is  of  universal  occurrence  through- 
out the  whole  vegetable  and  animal  kingdom,  we 
may  now  come  to  a  more  precise  and  clear  con- 
ception of  the  existing  differences  between  spe- 
cies and  varieties. 

For  this  purpose  we  must  take  a  somewhat 


Latent  Characters  221 

broader  view  of  the  whole  evolution  of  the 
vegetable  kingdom.  It  is  manifest  that  highly 
developed  plants  have  a  larger  number  of 
characters  than  the  lower  groups.  These 
must  have  been  acquired  in  some  way,  during 
preceding  times.  Such  evolution  must  evident- 
ly be  called  a  process  of  improvement,  or  a 
progressive  evolution.  Contrasted  to  this  is  the 
loss,  or  the  latency  of  characters,  and  this  may 
be  designated  retrogressive  or  retrograde  evo- 
lution. But  there  is  still  a  third  possibility. 
For  a  latent  character  may  reassume  its  ac- 
tivity, return  to  the  active  state,  and  become 
once  more  an  important  part  of  the  whole  or- 
ganization. This  process  may  be  designated 
as  degressive  evolution;  it  obviously  completes 
the  series  of  the  general  types  of  evolution. 

Advancement  in  general  in  living  nature  de- 
pends on  progressive  evolution.  In  different 
parts  of  the  vegetable  kingdom,  and  even  in 
different  families  this  progression  takes  place 
on  different  lines.  By  this  means  it  results  in 
an  ever  increasing  divergency  between  the  sev- 
eral groups.  Every  step  is  an  advance,  and 
many  a  step  must  have  been  taken  to  produce 
flowering  plants  from  the  simplest  unicellular 
algae. 

But  related  to,  and  very  intimately  con- 
nected with  this  advancement  is  the  retrogres- 


222  Retrograde  Varieties 

sive  evolution.  It  is  equally  universal,  per- 
haps never  failing.  No  great  changes  have 
been  attained,  without  acquiring  new  qualities 
on  one  side,  and  reducing  others  to  latency. 
Everywhere  such  retrogressions  may  be  seen. 
The  polypetalous  genera  Pyrola,  Ledum,  and 
Monotropa  among  the  sympetalous  heaths,  are 
a  remarkable  instance  of  this.  The  whole  evo- 
lution of  the  monocotyledons  from  the  lowest 
orders  of  dicotyledons  implies  the  seeming 
loss  of  cambial  growth  and  many  other  quali- 
ties. In  the  order  of  aroids,  from  the  cala- 
mus-root or  sweet  flag,  with  its  small  but  com- 
plete flowers,  up  to  the  reduced  duckweeds 
(Lemna),  almost  an  unbroken  line  of  interme- 
diate steps  may  be  traced  showing  everywhere 
the  concurrence  of  progressive  and  retrogres- 
sive evolution. 

Degressive  evolution  is  not  so  common  by  far, 
and  is  not  so  easy  to  recognize,  but  no  doubt  it 
occurs  very  frequently.  It  is  generally  called 
atavism,  or  better,  systematic  atavism,  and  the 
clearest  cases  are  those  in  which  a  quality  which 
is  latent  in  the  greater  part  of  a  family  or 
group,  becomes  manifest  in  one  of  its  members. 
Bracts  in  the  inflorescence  of  crucifers  are  or- 
dinarily wanting,  but  may  be  seen  in  some 
genera,  Erucastrum  pollichii  being  perhaps  the 


Latent  Characters  223 

most  widely  known  instance,  although  other 
cases  might  easily  be  cited. 

For  our  special  purpose  we  may  take  up 
only  the  more  simple  cases  that  may  be  avail- 
able for  experimental  work.  The  great  lines  of 
evolution  of  whole  families  and  even  of  genera 
and  of  many  larger  species  obviously  lie  outside 
the  limits  of  experimental  observation.  They 
are  the  outcome  of  the  history  of  the  ancestors 
of  the  present  types,  and  a  repetition  of  their 
history  is  far  beyond  human  powers.  We  must 
limit  ourselves  to  the  most  recent  steps,  to  the 
consideration  of  the  smallest  differences.  But 
it  is  obvious  that  these  may  be  included  under 
the  same  heads  as  the  larger  and  older  ones. 
For  the  larger  movements  are  manifestly  to  be 
considered  only  as  groups  of  smaller  steps, 
going  in  the  same  direction. 

Hence  we  conclude,  that  even  the  smallest 
steps  in  the  evolution  of  plants  which  we  are 
able  to  observe,  may  be  divided  into  progres- 
sive, retrogressive  and  degressive  ones.  The 
acquisition  of  a  single  new  quality  is  the  most 
simple  step  in  the  progressive  line,  the  becom- 
ing latent  and  the  reactivating  of  this  same 
quality  are  the  prototypes  of  the  two  other 
classes. 

Having  taken  this  theoretical  point  of  view, 
it  remains  to  inquire,  how  it  concurs  with  the 


224  Retrograde  Varieties 

various  facts,  given  in  former  lectures  and  how 
it  may  be  of  use  in  our  further  discussions. 

It  is  obvious  that  the  differences  between  ele- 
mentary species  and  varieties  on  the  one  hand, 
and  between  the  positive  and  negative  varieties 
as  distinguished  above,  are  quite  comparable 
with  our  theoretical  views.  For  we  have  seen 
that  varieties  can  always  be  considered  as  hav- 
ing originated  by  an  apparent  loss  of  some 
quality  of  the  species,  or  by  the  resumption  of 
a  quality  which  in  allied  species  is  present  and 
visible.  In  our  exposition  of  the  facts  we  have 
of  course  limited  ourselves  to  the  observable 
features  of  the  phenomena  without  searching 
for  a  further  explanation.  For  a  more  com- 
petent inquiry  however,  and  for  an  understand- 
ing of  wider  ranges  of  facts,  it  is  necessary  to 
penetrate  deeper  into  the  true  nature  of  the  im- 
plied causes. 

Therefore  we  must  try  to  show  that  elemen- 
tary species  are  distinguished  from  each  other 
by  the  acquisition  of  new  qualities,  and  that 
varieties  are  derived  from  their  species  either 
by  the  reduction  of  one  or  more  characteristics 
to  the  latent  state,  or  by  the  energizing  of  dor- 
mant characters. 

Here  we  meet  with  a  great  difficulty.  Hither- 
to varieties  and  subspecies  have  never  been 
clearly  defined,  or  when  they  have  been,  it  was 


Latent  Characters  225 

not  by  physiological,  but  only  by  morphological 
research.  And  the  claims  of  these  two  great 
lines  of  inquiry  are  obviously  very  diverging. 
Morphological  or  comparative  studies  need 
a  material  standard,  by  which  it  may  be  readily 
decided  whether  certain  groups  of  ani- 
mals and  plants  are  to  be  described  or  de- 
nominated as  species,  as  subspecies  or  as  varie- 
ties. To  get  at  the  inner  nature  of  the  dif- 
ferences is  in  most  cases  impossible,  but  a  de- 
cision must  be  made.  The  physiological  line 
of  inquiry  has  more  time  at  its  disposal ;  it  calls 
for  no  haste.  Its  experiments  ordinarily  cover 
years,  and  a  conclusion  is  only  to  be  reached 
after  long  and  often  weary  trials.  There  is  no 
making  a  decision  on  any  matter  until  all 
doubtful  points  have  been  cleared  up.  Of 
course,  large  groups  of  facts  remain  uncertain, 
awaiting  a  closer  inquiry,  and  the  teacher  is 
constrained  to  relv  on  the  few  known  instances 
of  thoroughly  investigated  cases.  These  alone 
are  safe  guides,  and  it  seems  far  better  to  trust 
to  them  and  to  make  use  of  them  for  the  con- 
struction of  sharp  conceptions,  which  may  help 
us  to  point  out  the  lines  of  inquiry  which  are 
still  open. 

Leaving  aside  all  such  divisions  and  defini- 
tions, as  were  stamped  with  the  name  of  pro- 
visional species  and  varieties  by  the  great  sys- 


226  Retrograde  Varieties 

tematist,  Alphonse  De  Candolle,  we  may  now 
try  to  give  the  proofs  of  our  assertion,  by  using 
only  those  instances  that  have  been  thoroughly 
tested  in  every  way. 

We  may  at  once  proceed  to  the  retrogressive 
or  negative  varieties.  The  arguments  for  the 
assumption  that  elementary  species  owe  their 
origin  to  the  acquisition  of  new  qualities  may 
well  be  left  for  later  lectures  when  we  shall 
deal  with  the  experimental  proofs  in  this  mat- 
ter. 

There  are  three  larger  groups  of  facts,  on 
which  the  assumption  of  latent  characters  in 
ordinary  varieties  rests.  These  are  true  ata- 
vism, incomplete  loss  of  characters,  and  system- 
atic affinity.  Before  dealing  with  each  of  these 
separately,  it  may  be  as  well  to  recall  once  more 
that  in  former  lectures  we  have  treated  the 
apparent  losses  only  as  modifications  in  a 
negative  way,  without  contemplating  the  under- 
lying causes. 

Let  us  recall  the  cases  of  bud-atavism  given 
by  the  whitish  variety  of  the  scarlet  Ribes,  by 
peaches  and  nectarines,  and  by  conifers,  includ- 
ing Ceplialotaxus  and  Cryptomeria.  These  and 
many  other  analogous  facts  go  to  prove  the  re- 
lation of  the  variety  to  the  species.  Two  as- 
sumptions are  allowable.  In  one  the  variety 
differs  from  the  species  by  the  total  loss  of  the 


Latent  Characters  227 

distinctive  character.  In  the  other  this  charac- 
ter is  simply  reduced  to  an  inactive  or  dormant 
state.  The  fact  of  its  recurrence  from  time  to 
time,  accompanied  by  secondary  characters 
previously  exhibited,  is  a  manifest  proof  of  the 
existence  of  some  relation  between  the  lost  and 
the  resumed  peculiarity.  Evidently  this  rela- 
tion cannot  be  accounted  for  on  the  assump- 
tion of  an  absolute  disappearance;  something 
must  remain  from  which  the  old  features  may 
be  restored. 

This  lengthy  discussion  may  be  closed  by  the 
citation  of  the  cases,  in  which  plants  not  only 
show  developmental  features  of  a  former  state, 
but  also  reproduce  the  special  features  they 
formerly  had,  but  seemingly  have  lost.  Two 
good  illustrative  examples  may  be  given.  One 
is  afforded  by  the  wheat-ear  carnation,  the 
other  by  the  greBn  dahlias,  and  both  have  oc- 
curred of  late  in  my  own  cultures. 

A  very  curious  anomaly  may  from  time  to 
time  be  observed  in  large  beds  of  carnations. 
It  bears  no  flowers,  but  instead  of  them  small 
green  ears,  which  recall  the  ears  of  wheat. 
Thence  the  name  of  *^  Wheat-ear  "  carnation. 
On  closer  inspection  it  is  easily  seen  how  they 
originate.  The  normal  flowers  of  the  carna- 
tions are  preceded  by  a  small  group  of  bracts, 


228  Retrograde  Varieties 

which  are  arranged  in  opposite  pairs  and  there- 
fore constitute  four  rows. 

In  this  variety  the  flower  is  suppressed  and 
this  loss  is  attended  hy  a  corresponding  in- 
crease of  the  number  of  the  pairs  of  bracts. 
This  malformation  results  in  square  spikes  or 
somewhat  elongated  heads  consisting  only  of 
the  greenish  bracts.  As  there  are  no  flowers, 
the  variety  is  quite  sterile,  and  as  it  is  not  re- 
garded by  horticulturists  as  an  improvement  on 
the  ordinary  bright  carnations,  it  is  seldom  mul- 
tiplied by  layering.  Notwithstanding  this,  it 
appears  from  time  to  time  and  has  been  seen  in 
different  countries  and  at  different  periods, 
and,  what  is  of  great  importance  for  us,  in  dif- 
ferent strains  of  carnations.  Though  sterile, 
and  obviously  dying  out  as  often  as  it  springs 
into  existence,  it  is  nearly  two  centuries  old. 
It  was  described  in  the  begining  of  the  18th  cen- 
tury by  Volckamer,  and  afterwards  by  Jaeger, 
De  Candolle,  Weber,  Masters,  Magnus  and 
many  other  botanists.  I  have  had  it  twice,  at 
different  times  and  from  different  growers. 

So  far  as  I  have  been  able  to  ascertain  re- 
versions of  this  curious  carnation  to  normal 
flowers  have  not  yet  been  recorded.  Such  a 
modification  occurred  last  summer  in  my  gar- 
den on  a  plant  which  had  not  been  divided  or 
layered,  but  on  which  the  slender  branches  had 


Latent  Characters  229 

been  left  on  the  stem.  Some  of  them  remained 
true  to  the  varietal  type  and  bore  only  green 
spikes.  Others  reverted  wholly  or  partially  to 
the  production  of  normal  flowers.  Some 
branches  bore  these  only,  others  had  spikes  and 
flowers  on  neighboring  twigs,  and  in  still  other 
instances  little  spikes  had  been  modified  in  such 
manner  that  a  more  or  less  well  developed  flow- 
er was  preceded  by  some  part  of  an  ear. 

The  proof  that  this  retrograde  modification 
was  due  to  the  existence  of  a  character  in  the 
latent  state  was  given  by  the  color  of  the  flow- 
ers. If  the  reverted  bud  had  only  lost  the 
power  of  producing  spikes,  they  would  evident- 
ly simply  have  returned  to  the  characteristics 
of  the  ordinary  species,  and  their  color  would 
have  been  a  pale  pink.  Instead  of  this,  all 
flowers  displayed  corollas  of  a  deep  brown. 
They  obviously  reverted  to  their  special  prog- 
enitor, the  chance  variety  from  which  they  had 
sprung,  and  not  to  the  common  prototype  of  the 
species.  Of  course  it  was  not  possible  to  as- 
certain from  which  variety  the  plant  had  really 
originated,  but  the  reproduction  of  any  one 
clearly  defined  varietal  mark  is  in  itself  proof 
enough  of  their  origin,  and  of  the  latency  of  the 
dark  brown  flower-color  in  this  special  case. 

A  still  better  proof  is  afforded  by  a  new  type 
of  green  dahlia.     The  ordinary  green  dahlia 


230  Retrograde  Varieties 

has  large  tufts  of  green  bracts  instead  of  flow- 
ering heads,  the  scales  of  the  receptacle  having 
assumed  the  texture  and  venation  of  leaves,  and 
being  in  some  measure  as  fleshy.  But  the 
green  heads  retain  the  form  of  the  ordinary 
flower-heads,  and  as  they  have  no  real  florets 
that  may  fade  away,  they  remain  unchanged  on 
the  plants,  and  increase  in  number  through  the 
whole  summer.  The  new  types  of  green  dahlia 
however,  with  which  I  have  now  to  deal,  are 
distinguished  by  the  elongation  of  the  axis  of  the 
head,  which  is  thereby  changed  into  a  long  leafy 
stalk,  attaining  a  length  of  several  inches. 
These  stalks  continue  growing  for  a  very  long 
time,  and  for  the  most  part  die  without  produc- 
ing anything  else  than  green  fleshy  scales. 

This  long-headed  green  dahlia  originated  at 
Haarlem  some  years  ago,  in  the  nursery  of 
Messrs.  Zocher  &  Co.  It  was  seen  to  arise 
twice,  from  different  varieties.  Both  of  these 
were  double-flowered,  one  a  deep  carmine  with 
white  tips  on  the  rays,  the  other  of  a  pale  orange 
tint,  known  by  the  name  of  ^^  Surprise."  As 
they  did  not  bear  any  florets  or  seeds,  they  were 
quite  sterile.  The  strain  arising  from  the  car- 
mine variety  was  kindly  given  to  me  by  Messrs. 
Zocher  &  Co.,  and  was  propagated  in  my  gar- 
den, while  the  other  was  kept  in  the  nursery. 
In  the  earlier  cultures  both  remained  true  to 


Latent  Characters  231 

their  types,  never  producing  true  florets.  No 
mark  of  the  original  difference  was  to  be  seen 
between  them.  But  last  summer  (1903)  both 
reverted  to  their  prototypes,  bearing  rela- 
tively large  numbers  of  ordinary  double  flower- 
heads  among  the  great  mass  of  green  stalks. 
Some  intermediate  forms  also  occurred  consist- 
ing of  green-scaled  stalks  ending  in  small  heads 
with  colored  florets. 

Thus  far  we  have  an  ordinary  case  of  rever- 
sion. But  the  important  side  of  the  phenome- 
non was,  that  each  plant  exactly  ^*  recollected  " 
from  which  parent  it  had  sprung.  All  of  those 
in  my  garden  reverted  to  the  carmine  florets 
with  white  tips,  and  all  of  those  in  the  nursery 
to  the  pale  orange  color  and  the  other  character- 
istics of  the  ^'  Surprise  "  variety. 

It  seems  absolutely  evident,  that  no  sunple 
loss  can  account  for  this  difference.  Something 
of  the  character  of  the  parent-varieties  must 
have  remained  in  the  plant.  And  whatever 
conception  we  may  formulate  of  these  vestigial 
characters  it  is  clear  that  the  simplest  and  most 
obvious  idea  is  their  preservation  in  a  dormant 
or  latent  state.  Assuming  that  the  distinguish- 
ing marks  have  only  become  inactive  by  vires- 
cence,  it  is  manifest  that  on  returning  each  will 
show  its  own  peculiarities,  as  recorded  above. 

Our  second  point  was  the  incomplete  loss  of 


232  Retrograde  Varieties 

the  distinguishing  quality  in  some  varieties.  It 
is  of  general  occurrence,  though  often  over- 
looked. Many  white  varieties  of  colored  flow- 
ers give  striking  instances,  among  them  many 
of  the  most  stable  and  most  prized  garden-flow- 
ers. If  you  look  at  them  separately  or  in  lit- 
tle bouquets  they  seem  to  be  of  irreproachable 
purity.  But  if  you  examine  large  beds  a  pale 
hue  will  become  visible.  In  many  cases  this 
tinge  is  so  slight  as  to  be  only  noticeable  in  a 
certain  illumination,  or  by  looking  in  an  oblique 
direction  across  the  bed;  in  others  it  is  at  once 
evident  as  soon  as  it  has  been  pointed  out.  It 
always  reminds  the  observer  of  the  color  of 
the  species  to  which  the  variety  belongs,  being 
bluish  in  violets  and  harebells,  reddish  in 
godetias  and  phloxes,  in  Silene  Armeria  and 
many  others.  It  proves  that  the  original  color- 
quality  of  the  species  has  not  wholly,  but  only 
partly  disappeared.  It  is  dormant,  but  not  en- 
tirely obliterated;  latent,  but  not  totally  con- 
cealed; inactive,  but  only  partially  so.  Our 
terminology  is  an  awkward  one;  it  practically 
assumes,  as  it  so  often  does  in  other  cases,  a 
conventional  understanding,  not  exactly  cor- 
responding to  the  simple  meaning  of  the  words. 
But  it  would  be  cumbrous  to  speak  always  of 
partial  inactivity,  incomplete  latency  or  half 
awakening  qualities.     Even  such  words  as  sub- 


Latent  Characters  233 

latent,  which  would  about  express  the  real  state 
of  things,  would  have  little  chance  of  coming 
into  general  use. 

Such  sub-latent  colors  are  often  seen  on  spe- 
cial parts  in  white  varieties  of  flowers.  In 
many  cases  it  is  the  outer  side  of  the  petals 
which  recalls  the  specific  color,  as  in  some  white 
roses.  In  violets  it  is  often  on  the  spur  that 
the  remains  of  the  original  pigment  are  to  be 
seen.  In  many  instances  it  is  on  the  tips  of 
the  petals  or  of  the  segments  of  the  corolla,  and 
a  large  number  of  white  or  yellow  flowers  be- 
tray their  affinity  to  colored  species  by  becom- 
ing red  or  bluish  at  the  edges  or  on  the  outer 
side. 

The  reality  of  such  very  slight  hues,  and  their 
relation  to  the  original  pigTQent  of  the  species 
may  in  some  cases  be  proved  by  direct  experi- 
ment. If  it  is  granted  that  latency  is  not  an  ab- 
solute quality,  then  it  will  be  readily  accepted, 
that  even  latency  must  be  subjected  to  the  laws 
of  gradual  variation  or  fluctuating  variability. 
We  will  deal  with  these  laws  in  a  later 
lecture  but  every  one  knows  that  greater  de- 
viations than  the  ordinary  may  be  attained  by 
sowing  very  large  numbers  and  by  selecting 
from  among  them  the  extreme  individuals  and 
sowing  anew  from  their  seed.  In  this  way  the 
slightest   tinge    of   any   latent    color   may   be 


234  Retrograde  Varieties 

strengthened,  not  indeed  to  the  restoration  of 
the  tinge  of  the  species,  but  at  least  so  far  as 
to  leave  no  doubt  as  to  the  identity  of  the  visi- 
ble color  of  the  species  and  the  latent  or  sub- 
latent  one  of  the  variety. 

I  made  such  an  experiment  with  the  peach- 
leaved  harebell  or  Campanula  persicifolia.  The 
white  variety  of  this  species,  which  is  often  met 
with  in  our  gardens,  shows  a  very  pale  bluish 
hue  when  cultivated  in  large  quantities,  which 
however  is  subject  to  individual  variations.  I 
selected  some  plants  with  a  decided  tinge, 
flowered  them  separately,  sowed  their  seeds, 
and  repeated  this  during  two  generations.  The 
result  was  an  increase  of  the  color  on  the  tips 
of  the  segments  of  the  corolla  in  a  few  in- 
dividuals, most  of  them  remaining  as  purely 
white  as  the  original  strain.  But  in  those  few 
plants  the  color  was  very  manifest,  individually 
variable  in  degree,  but  always  of  the  same  blue 
as  in  the  species  itself. 

Many  other  instances  could  be  given. 
Smooth  varieties  are  seldom  absolutely  so,  and 
if  scattering  hairs  are  found  on  the  leaves  or 
only  on  some  more  or  less  concealed  parts,  they 
correspond  in  their  character  to  those  of  the 
species.  So  it  is  with  prickles,  and  even  the 
thornless  thorn-apple  has  fruits  with  surfaces 
far  from   smooth.      The  thornless  horse-chest- 


Latent  Characters  235 

nut  has  in  some  instances  such  evident  protu- 
berances on  the  valves  of  its  fruits,  that  it  may 
seem  doubtful  whether  it  is  a  pure  and  stable 
variety. 

Systematic  latency  may  betray  itself  in  dif- 
ferent ways,  either  by  normal  systematic 
marks,  or  by  atavism.  With  the  latter  I  shall 
deal  at  length  on  another  occasion,  and  there- 
fore I  will  give  here  only  one  very  clear  and 
beautiful  example.  It  is  afforded  by  the  com- 
mon red  clover.  Obviously  the  clovers,  with 
their  three  leaflets  in  each  leaf,  stand  in  the 
midst  of  the  great  family  of  papilionaceous 
plants,the  leaves  of  which  are  generally  pinnate. 
Systematic  affinity  suggests  that  the  '^  three- 
leaved  "  forms  must  have  been  derived  from 
pinnate  ancestors,  evidently  by  the  reduction  of 
the  number  of  the  leaflets.  In  some  species  of 
clover  the  middle  of  the  three  is  more  or  less 
stalked,  as  is  ordinarily  the  case  in  pinnate 
leaves ;  in  others  it  is  as  sessile  as  are  its  neigh- 
bors. In  a  subsequent  chapter  I  will  describe  a 
very  fine  variety,  which  sometimes  occurs  in  the 
wild  state  and  may  easily  be  isolated  and  culti- 
vated. It  is  an  ordinary  red  clover  with  five 
leaflets  instead  of  three,  and  with  this  number 
varying  between  three  and  seven,  instead  of  be- 
ing nearly  wholly  stable  as  in  the  common  form. 
It  produces  from  time  to  time  pinnate  leaves, 


236  Retrograde  Varieties 

very  few  indeed,  and  only  rarely,  but  then  often 
two  or  three  or  even  more  on  the  same  in- 
dividual. Intermediate  stages  are  not  want- 
ing, but  are  of  no  consequence  here.  The  pin- 
nate leaves  obviously  constitute  a  reversion  to 
some  prototype,  to  some  ancestor  with  ordinary 
papilionaceous  leaves.  They  give  proof  of  the 
jDresence  of  the  common  character  of  the  fam- 
ily, concealed  here  in  a  latent  state.  Any 
other  explanation  of  this  curious  anomaly 
would  evidently  be  artificial.  On  the  other 
hand  nothing  is  really  known  about  the  ances- 
tors of  clover,  and  the  whole  conception  rests 
only  on  the  prevailing  views  of  the  systematic 
relationships  in  this  family.  But,  as  I  have  al- 
ready said,  further  proof  must  be  left  for  a  sub- 
sequent occasion. 

Many  instances,  noted  in  our  former  lectures, 
could  be  c|uoted  here.  The  systematic  distri- 
bution of  rayed  and  rayless  species  and  varie- 
ties among  the  daisy-group  of  the  composites 
affords  a  long  series  of  examples.  Accidental 
variations  in  both  directions  occur.  The  Can- 
ada fleabane  or  Erigeron  canadensis^  the  tansy 
or  Tanacetum  vidgare  and  some  others  may  at 
times  be  seen  with  ray-florets,  and  according 
to  Murr,  they  may  sometimes  be  wanting  in 
Aster  Tripolium,  Bellis  perennis,  some  species 
of  Anthemis,  Arnica  montana  and  in  a  number 


Latent  Characters  237 

of  other  well-known  rayed  species.  Another  in- 
stance may  be  quoted;  it  has  been  pointed  out 
by  Grant  Allen,  and  refers  to  the  dead-nettle  or 
Lamium  album.  Systematically  placed  in  a 
genus  with  red-flowering  species,  we  may  re- 
gard its  white  color  as  due  to  the  latency  of  the 
general  red  pigment.  But  if  the  flower  of  this 
plant  is  carefully  examined,  it  will  be  found  in 
most  cases  not  to  be  purely  white,  but  to  have 
some  dusky  lines  and  markings  on  its  lower  lip. 
Similar  devices  are  observed  on  the  lip  of  the 
allied  Lamium  maculatum^  and  in  a  less  de- 
gree on  the  somewhat  distant  Lamium  pur- 
pureum.  With  Lamium  maculatum  or  spotted 
dead-nettle,  the  affinity  is  so  close  that  even 
Bentham  united  the  two  in  a  single  species,  con- 
sidering the  ordinary  dead-nettle  only  as  a  va- 
riety of  the  dappled  purple  type.  For  the  sup- 
port of  this  conception  of  a  specific  or  varietal 
retrograde  change  many  other  facts  are  af- 
forded by  the  distribution  of  the  characteristic 
color  and  of  the  several  patterns  of  the  lips  of 
other  labiates,  and  our  general  understanding  of 
the  relationships  of  the  species  and  genera  in 
this  family  may  in  a  broad  sense  be  based  on  the 
comparison  of  these  seemingly  subordinate 
characteristics. 

The  same  holds  good  in  many  other  cases, 
and  systematists  have  often  become  uncertain 


238  Retrograde  Varieties 

as  to  the  true  value  of  some  form,  by  its  rela- 
tionship to  the  allied  types  in  the  way  of  retro- 
gressive modification.  Color-differences  are  so 
showy,  that  they  easily  overshadow  other  char- 
acters. The  white  and  the  blue  thorn-apple, 
the  white  and  the  red  campion  {Lychnis  ves- 
pertina  and  diurna)  and  many  other  illustrative 
cases  could  be  given,  in  which  two  forms  are 
specifically  separated  by  some  authors,  but 
combined  by  others  on  the  ground  of  the  retro- 
grade nature  of  some  differentiating  mark. 

Hitherto  we  have  dealt  with  negative  charac- 
ters and  tried  to  prove  that  the  conception  of 
latency  of  the  opposite  positive  characteristics 
is  a  more  natural  explanation  of  the  phenome- 
non than  the  idea  of  a  complete  loss.  We  have 
now  to  consider  the  positive  varieties,  and  to 
show  that  it  is  quite  improbable  that  here  the 
species  have  struck  out  for  themselves  a  wholly 
new  character.  In  some  instances  such  may 
have  been  the  case,  but  then  I  should  prefer  to 
treat  these  rather  as  elementary  species.  But 
in  the  main  we  will  have  to  assume  the  latency 
of  the  character  in  the  species  and  its  reassump- 
tion  by  the  variety  when  originating,  as  the  most 
probable  explanation. 

Great  stress  is  laid  upon  this  conception  by 
the  fact,  that  positive  varieties  are  so  exces- 
sively rare  when  compared  with  the  common  oc- 


Latent  Characters  239 

currence  of  negative  ones.  Indeed,  if  we  put 
aside  the  radiate  and  the  color-varieties  of 
flowers  and  foliage,  hardly  any  cases  can  be 
cited.  We  have  dealt  with  this  question  in  a 
former  lecture,  and  may  now  limit  ourselves  to 
the  positive  color-varieties. 

The  latency  of  the  faculty  of  producing  the 
red  pigment  in  leaves  must  obviously  be  ac- 
cepted for  nearly  the  whole  vegetable  kingdom. 
Oaks  and  elms,  the  beautiful  climbing  species 
of  Ampelopsis,  many  conifers,  as  for  instance 
Cryptomeria  japonica,  some  brambles,  the 
Guelder-rose  (Viburnum  Opulus)  and  many 
other  trees  and  shrubs  assume  a  more  or  less 
bright  red  color  in  the  fall.  During  summer 
this  tendency  must  have  been  dormant,  and  that 
this  is  so,  is  shown  by  the  young  leaves  of  oaks 
and  others,  which,  when  unfolding  in  the  spring 
show  a  similar  but  paler  hue.  Moreover,  there 
is  a  way  of  awakening  the  concealed  powers  at 
any  time.  We  have  only  to  inflict  small  wounds 
on  the  leaves,  or  to  cut  through  the  nerves  or  to 
injure  them  by  a  slight  bruising,  and  the  leaves 
frequently  respond  with  an  intense  reddening  of 
the  living  tissues  around  and  especially  above 
the  wounds.  Azolla  caroliniana,  a  minute  moss- 
like floating  plant  allied  to  the  ferns,  responds 
to  light  and  cold  with  a  reddish  tinge,  and  to 
shade  or  warmth  with  a  pure  green.     The  foli- 


240  Retrograde  Varieties 

age  of  many  other  plants  behaves  likewise,  as 
also  do  apples  and  peaches  on  the  insolated 
sides  of  the  fruits.  It  is  quite  impossible  to 
state  these  groups  of  facts  in  a  more  simple  way 
than  by  the  statement  that  the  tendency  to  be- 
come red  is  almost  generally  present,  though 
latent  in  leaves  and  stems^  and  that  it  comes 
into  activity  whenever  a  stimulus  provokes  it. 

Now  it  must  be  granted  that  the  energizing 
of  such  a  propensity  under  ordinary  circum- 
stances is  quite  another  thing  from  the  orig- 
ination of  a  positive  variety  by  the  evolution 
of  the  same  character.  In  the  variety  the  ac- 
tivity has  become  independent  of  outer  in- 
fluences or  dependent  upon  them  in  a  far  lesser 
degree.  The  power  of  producing  the  red  pig- 
ments is  shown  to  be  latent  by  the  facts  given 
above,  and  we  see  that  in  the  variety  it  is  no 
longer  latent  but  is  in  perfect  and  lasting  ac- 
tivity throughout  the  whole  life  of  the  plant. 

Red  varieties  of  white  flowers  are  much  more 
rare.  Here  the  latency  of  the  red  pigment  may 
be  deduced  partly  from  general  arguments  like 
those  just  given,  partly  from  the  special  syste- 
matic relations  in  the  given  cases.  Hildebrand 
has  clearly  worked  out  this  mode  of  proof.  He 
showed  by  the  critical  examination  of  a  large 
number  of  instances  that  the  occurrence  of  the 
red-flowered    varieties  is  contingent  upon  the 


Latent  Characters  241 

existence  of  red  species  in  the  same  genus,  or 
in  some  rare  cases,  in  nearly  allied  genera. 
Colors  that  are  not  systematically  present  in 
the  group  to  which  a  white  species  belongs  are 
only  produced  in  its  varieties  in  extremely  rare 
cases. 

We  may  quote  some  special  rules,  indicated 
by  Hildebrand.  Blue  species  are  in  the  main 
very  rare,  and  so  are  blue  varieties  of  white 
species  also.  Carnations,  Asiatic  or  cultivated 
buttercups  {Ranunculus  asiaticus),  Mirahilis, 
poppies,  Gladiolus,  Dahlia,  and  some  other 
highly  cultivated  or  very  old  garden-plants  have 
not  been  able  to  produce  true  blue  flowers.  But 
the  garden-anemone  {Anemone  coronaria)  has 
allies  with  very  fine  blue  flowers.  The  common 
stock  has  bluish  varieties  and  is  allied  to  Aiibre- 
tia  and  Hesperis,  and  gooseberries  have  a  red 
form,  recalling  the  ordinary  currant.  In  nearly 
all  other  instances  of  blue  or  red  varieties  every 
botanist  will  be  able  to  point  out  some  allied  red 
or  blue  species,  as  an  indication  of  the  probable 
source  of  the  varietal  character. 

Dark  spots  on  the  lower  parts  of  the  petals 
of  some  plants  afford  another  instance,  as  in 
poppies  and  in  the  allied  Glaucium,  where  they 
sometimes  occur  as  varietal  and  in  other  cases 
as  specific  marks. 

The  yellow  fails  in  many  highly  developed 


242  Retrograde  Varieties 

flowers,  which  are  not  liable  to  produce  yellow 
variations,  as  in  Salvia,  Aster,  Centaurea, 
Vinca,  Polygala  and  many  others.  Even  the 
rare  pale  yellowish  species  of  some  of  these 
genera  have  no  tendency  in  this  direction.  The 
hvacinths  are  the  most  remarkable,  if  not  the 
sole  known  instance  of  a  species  having  red  and 
blue  and  white  and  yellow  varieties,  but  here  the 
yellow  is  not  the  bright  golden  color  of  the  but- 
tercups. 

The  existence  of  varietal  colors  in  allied  spe- 
cies obviously  points  to  a  common  cause,  and 
this  cause  can  be  no  other  than  the  latency  of 
the  pigment  in  the  species  that  do  not  show  it. 

The  conception  of  latency  of  characters  as  the 
common  source  of  the  origination  of  varieties, 
either  in  the  positive  or  in  the  negative  way, 
leads  to  some  rules  on  variability,  which  are 
known  under  the  names  given  to  them  by  Dar- 
win. They  are  the  rules  of  repeated,  homolog- 
ous, parallel  and  analogous  variability.  Each 
of  them  is  quite  general,  and  may  be  recog- 
nized in  instances  from  the  most  widelv  dis- 

« 

tant  families.  Each  of  them  is  quite  evident 
and  easily  understood  on  the  principle  of 
latency. 

By  the  term  of  repeated  variability  is  meant 
the  well-known  phenomenon,  that  the  same  va- 
riety has  sprung  at  different  times  and  in  dif- 


Latent  Characters  243 

ferent  countries  from  the  same  species.  The 
repetition  obviously  indicates  a  common  inter- 
nal cause.  The  white  varieties  of  blue-  and  red- 
flowered  plants  occur  in  the  wild  state  so  often, 
and  in  most  of  the  instances  in  so  few  in- 
dividuals that  a  common  pedigree  is  absolutely 
improbable.  In  horticulture  this  tendency  is 
widely  and  vexatiously  known,  since  the  repeti- 
tion of  an  old  variety  does  not  bring  any  ad- 
vantage to  the  breeder.  The  old  name  of 
^^  conquests/'  given  by  the  breeders  of  hya- 
cinths, tulips  and  other  flower-bulbs  to  any 
novelty,  in  disregard  of  the  common  occurrence 
of  repetitions,  is  an  indication  of  the  same  ex- 
perience in  the  repeated  appearance  of  certain 
varieties. 

The  rule  of  parallel  variations  demands  that 
the  same  character  occasionally  makes  its  ap- 
pearance in  the  several  varieties  or  races,  de- 
scended from  the  same  species,  and  even  in 
widely  distinct  species.  This  is  a  rule,  which 
is  very  important  for  the  general  conception  of 
the  meaning  of  the  term  variety  as  contrasted 
with  elementary  species.  For  the  recurrence 
of  the  same  deviation  always  impresses  us  as  a 
varietal  mark.  Laciniated  leaves  are  perhaps 
the  most  beautiful  instance,  since  they  occur  in 
so  many  trees  and  shrubs,  as  the  walnut  tree, 
the  beech,  the  birch,  the  hazelnut,  and  even  in 


244  Retrograde  Varieties 

brambles  and  some  garden-varieties  of  the  tur- 
nip {Br  as  sic  a). 

In  such  cases  of  parallel  variations  the  single 
instances  obviously  follow  the  same  rules  and 
are  therefore  to  be  designated  as  analogous. 
Pitchers  or  ascidia,  formed  by  the  union  of  the 
margins  of  a  leaf,  are  perhaps  the  best  proof. 
They  were  classified  by  Morren  under  two  heads, 
according  to  their  formation  from  one  or  more 
leaves.  Monophyllous  pitchers  obey  the  same 
law,  viz. :  that  the  upper  side  of  the  leaf  has  be- 
come the  inner  side  of  the  pitcher.  Only  one 
exception  to  this  rule  is  known  to  me.  It  is  af- 
forded by  the  pitchers  of  the  banyan  or  holy 
fig-tree,  Ficus  religiosus,  but  it  does  not  seem  to 
belong  to  the  same  class  as  other  pitchers, 
since  as  far  as  it  has  been  possible  to  ascertain 
the  facts,  these  pitchers  are  not  formed  by  a 
few  leaves  as  in  all  other  cases,  but  by  all  the 
leaves  of  the  tree. 

In  some  cases  pitchers  are  only  built  up  of 
part  of  the  leaf-blade.  Such  partial  malforma- 
tions obey  a  rule,  that  is  common  to  them  and  to 
other  foliar  enations,  viz. :  that  the  side  of  the 
leaf  from  which  they  emerge,  is  always  their 
outer  side.  The  inner  surface  of  these  ena- 
tions corresponds  to  the  opposite  side  of  the 
leaf,  both  in  color  and  in  anatomical  structure. 

The  last  of  the  four  rules  above  mentioned  is 


Latent  Characters  245 

that  of  the  homologous  variability.  It  asserts 
that  the  same  deviation  may  occur  in  different, 
but  homologous  parts  of  the  same  plant.  We 
have  already  dealt  with  some  instances,  as  the 
occurrence  of  the  same  pigment  in  the  flowers 
and  foliage,  in  the  fruits  and  seeds  of  the  same 
plant,  as  also  illustrated  by  the  loss  of  the  red 
or  blue  tinge  by  flowers  and  berries.  Other  in- 
stances are  afforded  by  the  curious  fact  that 
the  division  of  the  leaves  into  numerous  and 
small  segments  is  repeated  by  the  petals,  as 
in  the  common  celandine  and  some  sorts  of 
brambles. 

It  would  take  too  long  to  make  a  closer  exam- 
ination of  the  numerous  cases  which  afford 
proof  of  these  statements.  Suffice  it  to  say  that 
everywhere  the  results  of  close  inspection  point 
to  the  general  rule,  that  the  failure  of  definite 
qualities  both  in  species  and  in  varieties  must, 
in  a  great  number  of  cases,  be  considered  as  only 
apparent.  Hidden  from  view,  occasionally  re- 
appearing, or  only  imperfectly  concealed,  the 
same  character  must  be  assumed  to  be  present 
though  latent. 

In  the  case  of  negative  or  retrogressive  varie- 
ties it  is  the  transition  from  the  active  into  a 
dormant  state  to  which  is  due  the  origin  of  the 
variety.  Positive  varieties  on  the  contrary  owe 
their  origin  to  the  presence  of  some  character 


246  Retrograde  Varieties 

in  the  species  in  the  latent  state,  and  to  the  oc- 
casional re-energizhig  thereof. 

Specific  or  varietal  latency  is  not  the  same 
thing  as  the  ordinary  latency  of  characters  that 
only  await  their  period  of  activity,  or  the  ex- 
ternal influence  which  will  awake  them.  They 
are  permanently  latent,  and  could  well  be  des- 
ignated by  the  word  perlatent.  They  spring 
into  activity  only  by  some  sudden  leap,  and  then 
at  once  become  independent  of  ordinary  exter- 
nal stimulation. 


•">  ?;"'4'Jfi  '■?/ 


Lecture  IX 

CROSSES  OF  SPECIES  AND  VARIETIES 

In  the  foregoing  lectures  I  have  tried  to  show 
that  there  is  a  real  difference  between  element- 
ary species  and  varieties.  The  first  are  of 
equal  rank,  and  together  constitute  the  col- 
lective or  systematic  species.  The  latter  are 
usually  derived  from  real  and  still  existing 
types.  Elementary  species  are  in  a  sense  inde- 
pendent of  each  other,  while  varieties  are  of  a 
derivative  nature. 

Furthermore  I  have  tried  to  show  that  the 
ways  in  which  elementary  or  minor  species  must 
have  originated  from  their  common  ancestor 
must  be  quite  different  from  the  mode  of  origin 
of  the  varieties.  We  have  assumed  that  the 
first  come  into  existence  by  the  production  of 
something  new,  by  the  acquirement  of  a  char- 
acter hitherto  unnoticed  in  the  line  of  their  an- 
cestors. On  the  contrary,  varieties,  in  most 
cases,  evidently  owe  their  origin  to  the  loss  of 
an  already  existing  character,  or  in  other  less 
frequent  cases,  to  the  re-assumption  of  a  quality 

247 


248  Retrograde  Varieties 

formerly  lost.  Some  may  originate  in  a 
negative,  others  in  a  positive  manner,  but  in 
both  cases  nothing  really  new  is  acquired. 

This  distinction  holds  good  for  all  cases  in 
which  the  relationship  between  the  forms  in 
question  is  well  known.  It  seems  entirely  justi- 
fiable therefore  to  apply  it  also  to  cases  in 
which  the  systematic  affinity  is  doubtful,  as  well 
as  to  instances  in  which  it  is  impossible  to  ar- 
rive at  any  taxonomic  conclusions.  The  ex- 
treme application  of  the  principle  would  no 
doubt  disturb  the  limits  between  many  species 
and  varieties  as  now  recognized.  It  is  not  to  be 
forgotten  however  that  all  taxonomic  distinc- 
tions, which  have  not  been  confirmed  by  physi- 
ologic tests  are  only  provisional,  a  view  ac- 
knowledged by  the  best  systematists.  Of  course 
the  description  of  newly  discovered  forms  can 
not  await  the  results  of  physiologic  inquiries, 
but  it  is  absolutely  impossible  to  reach  definite 
conclusions  on  purely  morphologic  evidence. 
This  is  well  illustrated  by  the  numerous  dis- 
cords of  opinion  of  different  authors  on  the  sys- 
tematic worth  of  many  forms. 

Assuming  the  above  mentioned  principle  as 
established,  and  disregarding  doubtful  cases  as 
indicated,  the  term  progressive  evolution  is 
used  to  designate  the  method  in  which  element- 
ary species  must  have  originated.     It  is  the 


Unbalanced  Crosses  249 

manner  in  which  all  advance  in  the  animal  and 
vegetable  kingdoms  must  have  taken  place ;  con- 
tinuously adding  new  characters  to  the  already 
existing  number.  Contrasted  with  this  method 
of  growing  differentiation,  are  the  retrogres- 
sive modifications,  which  simply  retrace  a 
step,  and  the  degressive  changes  in  which 
a  backward  step  is  retraced  and  old  characters 
revived.  No  doubt  both  of  these  methods  have 
been  operative  on  a  large  scale,  but  they  are  evi- 
dently not  in  the  line  of  general  advancement. 

In  all  of  these  directions  we  see  that  the  dif- 
ferentiating marks  show  more  or  less  clearly 
that  they  are  built  up  of  units.  Allied  forms 
are  separated  from  each  other  without  interme- 
diates. Transitions  are  wholly  wanting,  al- 
though fallaciously  apparent  in  some  instances 
owing  to  the  wide  range  of  fluctuating  variabil- 
ity of  the  forms  concerned,  or  to  the  occurrence 
of  hybrids  and  subvarieties. 

These  physiologic  units,  which  in  the  end 
must  be  the  basis  for  the  distinction  of  the  sys- 
tematic units,  may  best  be  designated  by  the 
term  of  ' '  unit-characters. ' '  Their  internal  na- 
ture is  as  yet  unknown  to  us,  and  we  will  not 
now  look  into  the  theories,  which  have  been  pro- 
pounded as  to  the  probable  material  basis  un- 
derlying them.  For  our  present  purpose  the 
empirical  evidence  of  the  general  occurrence  of 


250  Retrograde  Varieties 

sharp  limits  between  nearly  related  characters 
must  suffice.  As  Bateson  has  put  it,  species  are 
discontinuous,  and  we  must  assume  that  their 
characters  are  discontinuous  also. 

Moreover  there  is  as  yet  no  reason  for  trying 
to  make  a  complete  analysis  of  all  the  charac- 
ters of  a  plant.  No  doubt,  if  attained,  such  an 
analysis  would  give  us  a  deep  insight  into  the 
real  internal  construction  of  the  intricate  prop- 
erties of  organisms  in  general.  But  taxonomic 
studies  in  this  direction  are  onlj^  in  their  in- 
fancy and  do  not  give  us  the  material  required 
for  such  an  analysis.  Quite  on  the  contrary, 
they  compel  us  to  confine  our  study  to  the  most 
recently  acquired,  or  youngest  characters, 
which  constitute  the  differentiating  marks  be- 
tween nearly  allied  forms. 

Obviously  this  is  especially  the  case  in  the 
realm  of  the  hybrids,  since  only  nearly  related 
forms  are  able  to  give  hybrid  offspring.  In 
dealing  with  this  subject  we  must  leave  aside 
all  questions  concerning  more  remote  relation- 
ships. 

It  is  not  my  purpose  to  treat  of  the  doctrine 
of  hybridization  at  any  length.  Experience  is 
so  rapidly  increasing  both  in  a  practical 
and  in  a  purely  scientific  direction  that  it  would 
take  an  entire  volume  to  give  only  a  brief  sur- 
vey of  the  facts  and  of  all  the  proposed  theories. 


Unbalanced  Crosses  251 

For  our  present  purposes  we  are  to  deal  with 
hybrids  only  in  so  far  as  they  afford  the  means 
of  a  still  better  distinction  between  elementary 
species  and  varieties.  I  will  try  to  show  that 
these  two  contrasting  groups  behave  in  quite  a 
different  manner,  when  subjected  to  crossing 
experiments,  and  that  the  hope  is  justified 
that  some  day  crosses  may  become  the  means  of 
deciding  in  any  given  instance,  what  is  to  be 
called  a  species,  and  what  a  variety,  on  physio- 
logic grounds.  It  is  readily  granted  that  the 
labor  required  for  such  experiments,  is  perhaps 
too  great  for  the  results  to  be  attained,  but  then 
it  may  be  possible  to  deduce  rules  from  a  small 
series  of  experiments,  which  may  lead  us  to  a 
decision  in  wider  ranges  of  cases. 

To  reach  such  a  point  of  view  it  is  necessary 
to  compare  the  evidence  given  by  hybrids,  with 
the  conclusions  alreadv  attained  by  the  com- 
parison  of  the  differentiating  characteristics  of 
allied  forms. 

On  this  ground  we  first  have  to  inquire  what 
may  be  expected  respecting  the  internal  nature 
and  the  outcome  of  the  process  of  crossing  in 
the  various  cases  cited  in  our  former  discussion. 

We  must  alwa5^s  distinguish  the  qualities, 
which  are  the  same  in  both  parents,  from  those 
that  constitute  the  differentiating  marks  in 
every   single    cross.     In    respect   to    the   first 


252  Retrograde  Varieties 

group  the  cross  is  not  at  all  distinguished  from 
a  normal  fertilization,  and  ordinarily  these 
characters  are  simply  left  out  of  consideration. 
But  it  should  never  be  forgotten  that  they  con- 
stitute the  enormous  majority,  amounting  to 
hundreds  and  thousands,  whereas  the  differen- 
tiating marks  in  each  case  are  only  one  or  two 
or  a  few  at  most.  The  whole  discussion  is  to 
be  limited  to  these  last-named  exceptions.  We 
must  consider  first  what  would  be  the  nature  of 
a  cross  when  species  are  symmetrically  com- 
bined, and  what  must  be  the  case  when  varieties 
are  subjected  to  the  same  treatment.  In  so  do- 
ing, I  intend  to  limit  the  discussion  to  the  most 
typical  cases.  We  may  take  the  crosses  between 
elementary  species  of  the  same  or  of  very  nar- 
rowly allied  systematic  species  on  the  one  side, 
and  on  the  other,  limit  treatment  to  the  crossing 
of  varieties  with  the  species,  from  which  they 
are  supposed  to  have  sprung  by  a  retrograde 
modification.  Crosses  of  different  varieties  of 
the  same  species  with  one  another  obviously 
constitute  a  derivative  case,  and  should  only  be 
discussed  secondarily.  And  crosses  of  varie- 
ties with  positive  or  degressive  characters  have 
as  yet  so  rarely  been  made  that  we  may  well 
disregard  them. 

Elementary  species  differ  from  their  nearest 
allies  by  progressive  changes,  that  is  by  the  ac- 


Unbalanced  Crosses  253 

quirement  of  some  new  character.  The  deriva- 
tive species  has  one  unit  more  than  the  parent. 
All  other  qualities  are  the  same  as  in  the  par- 
ent. Whenever  such  a  derivative  is  combined 
with  its  parent  the  result  for  these  qualities 
will  be  exactlv  as  in  a  normal  fertilization.  I71 
such  ordinary  cases  it  is  obvious  that  each  char- 
acter of  the  pollen-parent  is  combined  with  the 
same  character  of  the  pistil-parent.  There  may 
be  slight  individual  differences,  but  each  unit- 
character  will  become  opposed  to,  and  united 
with,  the  same  unit-character  in  the  other  par- 
ent. In  the  offspring  the  units  will  thus 
be  paired,  each  pair  consisting  of  two  equivalent 
units.  As  to  their  character  the  units  of  each 
single  pair  are  the  same,  only  they  may  exhibit 
slight  differences  as  to  the  degree  of  develop- 
ment of  this  character. 

Now  we  may  apply  this  conception  to  the  sex- 
ual combination  of  two  different  elementary 
species,  assuming  one  to  be  the  derivative  of 
the  other.  The  differentiating  mark  is  only 
present  in  one  of  the  parents  and  wanting  in  the 
other.  While  all  other  units  are  paired  in  the 
hybrid,  this  one  is  not.  It  meets  with  no  mate, 
and  must  therefore  remain  unpaired.  The 
hybrid  of  two  such  elementarj^  species  is  in 
some  way  incomplete  and  unnatural.  In  the 
ordinary  course  of  things  all  individuals  derive 


254  Retrograde  Varieties 

their  qualities  from  both  parents;  for  each  sin- 
gle mark  they  possess  at  least  two  units.  Prac- 
tically but  not  absolutely  equal,  these  two  op- 
ponents always  work  together  and  give  to  the 
offspring  a  likeness  to  both  parents.  No  un- 
paired qualities  occur  in  normal  offspring ;  these 
constitute  the  essential  features  of  the  hybrids 
of  species  and  are  at  the  same  time  the  cause  of 
their  wide  deviations  from  the  ordinary  rules. 

Turning  now  to  the  varieties,  we  likewise 
need  discuss  their  differentiating  marks  only. 
In  the  negative  types,  these  consist  of  the  ap- 
parent loss  of  some  quality  which  was  active  in 
the  species.  But  it  was  pointed  out  in  our  last 
lecture  that  such  a  change  is  an  apparent  loss. 
On  a  closer  inquiry  we  are  led  to  the  assumption 
of  a  latent  or  dormant  state.  The  presumably 
lost  characters  have  not  absolutelv,  or  at  least 
not  permanently  disappeared.  They  show 
their  presence  by  some  slight  indication  of  the 
quality  they  represent,  or  by  occasional  revers- 
ions.    They  are  not  wanting,  but  only  latent. 

Basing  our  discussion  concerning  the  process 
of  crossing  on  this  conception,  and  still  limiting 
the  discussion  to  one  differentiating  mark,  we 
come  to  the  inference,  that  this  mark  is  present 
and  active  in  the  species,  and  present  but  dor- 
mant in  the  variety.  Thus  it  is  present  in  both, 
and  as  all  other  characters  not  differentiating 


Unbalanced  Crosses  255 

find  their  mates  in  the  cross,  so  these  two  will 
also  meet  one  another.  They  will  unite  just  as 
well  as  though  they  were  both  active  or  both 
dormant.  For  essentially  they  are  the  same, 
only  differing  in  their  degree  of  activity.  From 
this  we  can  infer,  that  in  the  crossing  of  varie- 
ties, no  unpaired  remainder  is  left,  all  units 
combining  in  pairs  exactly  as  in  ordinary  fertil- 
ization. 

Setting  aside  the  contrast  between  activity 
and  latency  in  this  single  pair,  the  procedure  in 
the  inter-crossing  of  varieties  is  the  same  as  in 
ordinary  normal  fertilization. 

Summarizing  this  discussion  we  may  con- 
clude that  in  normal  fertilization  and  in  the 
inter-crossing  of  varieties  all  characters  are 
paired,  while  in  crosses  between  elementary 
species  the  differentiating  marks  are  not  mated. 

In  order  to  distinguish  these  two  great  types 
of  fertilization  we  will  use  the  term  bisexual  for 
the  one  and  unisexual  for  the  other.  The  term 
halanc,ed  crosses  then  conveys  the  idea  of  com- 
plete bisexuality,  all  unit-characters  combining 
in  pairs.  Unbalanced  crosses  are  those  in  which 
one  or  more  units  do  not  find  their  mates  and 
therefore  remain  unpaired.  This  distinction 
was  proposed  by  Macfarlane  when  studying 
the  minute  structure  of  plant-hybrids  in  com- 
parison with  that  of  their  parents  (1892). 


256  Retrograde  Varieties 

In  the  first  place  it  shows  that  a  species- 
hybrid  may  inherit  the  distinguishing  marks 
of  both  parents.  In  this  way  it  may  become  in- 
termediate between  them,  having  some  charac- 
ters in  common  with  the  pollen-parent  and  others 
with  the  pistil-parent.  As  far  as  these  charac- 
ters do  not  interfere  with  each  other,  they  may 
be  fnlly  developed  side  by  side,  and  in  the  main 
this  is  the  way  in  which  hybrid  characters  are 
evolved.  But  in  most  cases  our  existing  knowl- 
edge of  the  units  is  far  too  slender  to  give  a 
complete  analysis,  even  of  these  distinguishing 
marks  alone.  We  recognize  the  parental  marks 
more  or  less  clearly,  but  are  not  prepared  for 
exact  delimitations.  Leaving  these  theoretical 
considerations,  we  will  pass  to  the  description 
of  some  illustrative  examples. 

In  the  first  place  I  will  describe  a  hybrid 
between  two  species  of  Oenothera,  which  I 
made  some  years  ago.  The  parents  were  the 
common  evening-primrose  or  Oenothera  bien- 
nis and  of  its  small-flowered  congener,  Oeno- 
thera miiricata.  These  two  forms  were  distin- 
guished by  Linnaeus  as  different  species,  but 
have  been  considered  by  subsequent  writers  as 
elementary  species  or  so-called  systematic  va- 
rieties of  one  species  designated  with  the  name 
of  the  presumably  older  type,  the  0.  biennis. 
Varietal  differences  in  a  physiologic  sense  they 


Unbalanced  Crosses  257 

do  not  possess,  and  for  this  reason  afford  a 
pure  instance  of  unbalanced  union,  though  dif- 
fering in  more  than  one  point. 

I  have  made  reciprocal  crosses,  taking  at  one 
time  the  small-flowered  and  at  the  other  the 
common  species  as  pistillate  parent.  These 
crosses  do  not  lead  to  the  same  hybrid  as  is 
ordinarily  observed  in  analogous  cases ;  quite  on 
the  contrary,  the  two  types  are  different  in  most 
features,  both  resembling  the  pollen-parent 
far  more  than  the  pistil-parent.  The  same 
curious  result  was  reached  in  sundry  other  re- 
ciprocal crosses  between  species  of  this  genus. 
But  I  will  limit  myself  here  to  pne  of  the  two 
hybrids. 

In  the  summer  of  1895  I  castrated  some  flow- 
ers of  0.  muricata,  and  pollinated  them  with  0. 
hienniSj  surrounding  the  flowers  with  paper 
bags  so  as  to  exclude  the  visits  of  insects.  I 
sowed  the  seeds  in  1896  and  the  hybrids  were 
biennial  and  flowered  abundantly  the  next  year 
and  were  artificially  fertilized  with  their  own 
pollen,  but  gave  only  a  very  small  harvest. 
Many  capsules  failed,  and  the  remaining  con- 
tained only  some  few  ripe  seeds. 

From  these  I  had  in  the  following  year  the 
second  hybrid  generation,  and  in  the  same  way 
I  cultivated  also  the  third  and  fourth.  Tliese 
were  as  imperfectly  fertile  as  the  first,  and  in 


258  Retrograde  Varieties 

some  years  did  not  give  any  seed  at  all,  so  that 
the  operation  had  to  be  repeated  in  order  to 
continue  the  experiment.  Last  summer  (1903) 
I  had  a  nice  lot  of  some  25  biennial  specimens 
blooming  abundantly.  All  in  all  I  have  grown 
some  500  hybrids,  and  of  these  about  150  speci- 
mens flowered. 

These  plants  were  all  of  the  same  type,  re- 
sembling in  most  points  the  pollen-parent,  and 
in  some  others  the  pistil-parent  of  the  original 
cross.  The  most  obvious  characteristic  marks 
are  afforded  by  the  flowers,  which  in  0.  muri- 
cata  are  not  half  so  large  as  in  biennis, 
though  borne  by  a  calyx-tube  of  the  same 
length.  In  this  respect  the  hybrid  is  like  the 
biennis  bearhig  the  larger  flowers.  These  may 
at  times  seem  to  deviate  a  little  in  the  direction 
of  the  other  parent,  being  somewhat  smaller 
and  of  a  slightly  paler  color.  But  it  is  very 
difficult  to  distinguish  between  them,  and  if 
biennis  and  hybrid  flowers  were  separated  from 
the  plants  and  thrown  together,  it  is  very  doubt- 
ful whether  one  would  succeed  in  separating 
them. 

The  next  point  is  offered  by  the  foliage.  The 
leaves  of  0.  biennis  are  broad,  those  of  0.  muri- 
cata  narrow.  The  hvbrid  has  the  broad  leaves 
of  0.  biennis  during  most  of  its  life  and  at  the 
time  of  flowerinc:.     Yet  small  deviations  in  the 


Unbalanced  Crosses  259 

direction  of  the  other  parent  are  not  wanting, 
and  in  winter  the  leaves  of  the  hvbrid  rosettes 
are  often  much  narrower  than  those  of  0.  bien- 
nis, and  easily  distinguishable  from  both  par- 
ents. A  third  distinction  consists  in  the  den- 
sity of  the  spike.  The  distance  between  the  in- 
sertion of  the  flowers  of  0.  biennis  is  great  when 
compared  with  that  of  0.  muricata.  Hence  the 
flowers  of  the  latter  species  are  more  crowded 
and  those  of  0.  biennis  more  dispersed,  the 
spikes  of  the  first  being  densely  crowned  with 
flowers  and  flower-buds  while  those  of  0.  biennis 
are  more  elongated  and  slender.  As  a  further 
consequence  the  0.  biennis  opens  on  the  same 
evening  only  one,  two  or  three  flowers  on  the 
same  spike,  whereas  0.  muricata  bears  often 
eight  or  ten  or  more  flowers  at  a  time.  In  this 
respect  the  hybrid  is  similar  to  the  pistil-parent, 
and  the  crowding  of  the  broad  flowers  at  the 
top  of  the  spikes  causes  the  hybrids  to  be  much 
more  showy  than  either  of  the  parent  types. 

Other  distinguishing  marks  are  not  recorded 
by  the  systematists,  or  are  not  so  sharply  sepa- 
rated as  to  allow  of  the  corresponding  qualities 
of  the  hybrids  being  compared  with  them. 

This  hybrid  remains  true  to  the  description 
given.     In  some  years  I  cultivated  two  gener- 


260  Retrograde  Varieties 

ations  so  as  to  be  able  to  compare  them  with 
one  another,  but  did  not  find  any  difference. 
The  most  interesting  point  however,  is  the  like- 
ness between  the  first  generation,  which  ob- 
viously must  combine  in  its  internal  structure 
the  units  of  both  parents,  and  the  second  and 
later  generations  which  are  only  of  a  derivative 
nature.  Next  to  this  stands  the  fact  that  in 
each  generation  all  individuals  are  alike.  No 
reversion  to  the  parental  forms  either  in  the 
whole  type  or  in  the  single  characteristics  has 
ever  been  observed,  though  the  leaves  of  some 
hundreds,  and  the  spikes  and  flowers  of  some 
150  individual  plants  have  been  carefully  ex- 
amined. No  segregation  or  splitting  up  takes 
place. 

Here  we  have  a  clear,  undoubted  and  rela- 
tively simple,  case  of  a  true  and  pure  species- 
hybrid.  No  occurrence  of  possible  varietal 
characteristics  obscures  the  result,  and  in  this 
respect  this  hybrid  stands  out  much  more 
clearly  than  all  those  between  garden-plants, 
where  varietal  marks  nearly  always  play  a  most 
important  part. 

From  the  breeder's  point  of  view  our  hybrid 
Oenothera  would  be  a  distinct  gain,  were  it  not 
for  the  difficulty  of  its  propagation.  But  to  en- 
large the  range  of  the  varieties  this  simple  and 
stable  form  would  need  to  be  treated  anew,  by 


Unbalanced  Crosses  261 

crossing  it  with  the  parent-types.  Such  experi- 
ments however,  have  miscarried  owing  to  the 
too  stable  nature  of  the  unit-characters. 

This  stability  and  this  absence  of  the  split- 
ting shown  by  varietal  marks  in  the  offspring 
of  hybrids  is  one  of  the  best  proofs  of  unisex- 
ual unions.  It  is  often  obscured  by  the  accom- 
panying varietal  marks,  or  overlooked  for  this 
reason.  Only  in  rare  cases  it  is  to  be  met  with 
in  a  pure  state  and  some  examples  are  given  of 
this  below. 

Before  doing  so,  I  must  call  your  attention 
to  another  feature  of  the  unbalanced  unions. 
This  is  the  diminution  of  the  fertility,  a  phe- 
nomenon universally  known  as  occurring  in 
hybridizations.  It  has  two  phases.  First,  the 
diminished  chance  of  the  crosses  themselves  of 
giving  full  crops  of  seed,  as  compared  with  the 
pure  fertilization  of  either  parent.  And,  sec- 
ondly, the  fertility  of  the  hybrids  themselves. 
Seemingly,  all  grades  of  diminished  fertility 
occur  and  the  oldest  authors  on  hybrids  have 
pointed  out  that  a  very  definite  relation  exists 
between  the  differences  of  the  parents  and  the 
degree  of  sterility,  both  of  the  cross  and  of  the 
hybrid  offspring.  In  a  broad  sense  these  two 
factors  are  proportionate  to  each  other,  the 
sterility  being  the  greater,  the  lesser  the  affin- 
ity between  the  parents.     Many  writers  have 


262  Retrograde  Varieties 

tried  to  trace  this  rule  in  the  single  cases,  but 
have  met  with  nearly  unsurmountable  difficul- 
ties, owing  chiefly  to  our  ignorance  of  the  units 
which  form  the  differences  between  the  parents 
in  the  observed  cases. 

In  the  case  of  Oenothera  muricata  x  hlen- 
nis  the  differentiating  units  reduce  the  fertility 
to  a  low  degree,  threatening  the  offspring  with 
almost  complete  infertility  and  extinction. 
But  then  we  do  not  know  whether  these  charac- 
ters are  really  units,  or  perhaps  only  seemingly 
so  and  are  in  reality  composed  of  smaller  en- 
tities which  as  yet  we  are  not  able  to  segregate. 
And  as  long  as  we  are  devoid  of  empirical  means 
of  deciding  such  questions,  it  seems  useless  to  go 
farther  into  the  details  of  the  question  of  the 
sterility.  It  should  be  stated  here  however, 
that  pure  varietal  crosses,  when  not  accompan- 
ied by  unbalanced  characters,  have  never  showed 
any  tendency  to  diminished  fertility.  Hence 
there  can  be  little  doubt  that  the  unpaired  units 
are  the  cause  of  this  decrease  in  reproductive 
power. 

The  genus  Oenothera  is  to  a  large  degree  de- 
void of  varietal  characteristics,  especially  in 
the  subgenus  Onagra,  to  which  biennis,  mur- 
icata, lamarckiana  and  some  others  belong. 
On  the  other  hand  it  seems  to  be  rich  in 
elementary  species,  but  an  adequate  study  of 


I  )/••"» 


Unbalanced  Crosses  26 

them  has  as  yet  not  been  made.  Unfortunately 
many  of  the  better  systematists  are  in  the  habit 
of  throwing  all  these  interesting  forms  to- 
gether, and  of  omitting  their  descriptive  study. 
I  have  made  a  large  number  of  crosses  be- 
tween such  undescribed  types  and  as  a  rule 
got  constant  hybrid  races.  Only  one  or  two 
exceptions  could  be  quoted,  as  for  instance  the 
Oenothera  brevistylis,  which  in  its  crosses  al- 
ways behaves  as  a  pure  retrogressive  variety. 
Instead  of  giving  an  exhaustive  survey  of 
hybrids,  I  simply  cite  my  crosses  between 
lamarckiana  and  biennis,  as  having  nearly  the 
aspect  of  the  last  named  species,  and  remaining 
true  to  this  in  the  second  generation  without 
any  sign  of  reversion  or  of  splitting.  I  have 
crossed  another  elementary  species,  the  Oeno- 
thera hirtella  with  some  of  my  new  and  with 
some  older  Linnean  species,  and  got  several 
constant  hybrid  races.  Among  these  the  off- 
spring of  a  cross  between  muricata  and  hirtella 
is  still  in  cultivation.  The  cross  was  made  in 
the  summer  of  1897  and  last  year  (1903)  I  grew 
the  fourth  generation  of  the  h^-brids.  These 
had  the  characters  of  the  muricata  in  their  nar- 
row leaves,  but  the  elongated  spikes  and  rela- 
tively large  flowers  of  the  hirtella  parent,  and 
remained  true  to  this  type,  showing  only  slight 
fluctuations  and  never  reverting  or  segregating 


264  Retrograde  Varieties 

the  mixed  characters.  Both  parents  bear  large 
capsules  with  an  abundance  of  seed,  but  in  the 
hybrids  the  capsules  remain  narrow  and  weak, 
ripening  not  more  than  one-tenth  the  usual 
quantity  of  seed.  Both  parents  are  easily 
cultivated  in  annual  generations  and  the  same 
holds  good  for  the  hybrid.  But  whereas  the 
hybrid  of  muricata  and  biennis  is  a  stout  plant, 
this  type  is  weak  with  badly  developed  foliage, 
and  very  long  strict  spikes.  Perhaps  it  was 
not  able  to  withstand  the  bad  weather  of  the 
last  few  years. 

A  goodly  number  of  constant  hybrids  are  de- 
scribed in  literature,  or  cultivated  in  fields  and 
gardens.  In  such  cases  the  essential  question 
is  not  whether  they  are  now  constant,  but 
whether  they  have  been  so  from  the  beginning, 
or  whether  they  prove  to  be  constant  whenever 
the  original  cross  is  repeated.  For  constant 
hybrids  may  also  be  the  issue  of  incipient  split- 
tings, as  we  shall  soon  see. 

Among  other  examples  we  may  begin  with 
the  hybrid  alfalfa  or  hybrid  lucerne  (Medicago 
media).  It  often  originates  spontaneously  be- 
tween the  common  purple  lucerne  or  alfalfa 
and  its  wild  ally  with  yellow  flowers  and  pro- 
cumbent stems,  the  Medicago  falcata.  This 
hybrid  is  cultivated  in  some  parts  of  Germany 
on  a  large  scale,  as  it  is  more  productive  than 


Unbalanced  Crosses  265 

the  ordinary  lucerne.  It  always  comes  true 
from  seed  and  may  be  seen  in  a  wild  state  in 
parks  and  on  lawns.  It  is  one  of  the  oldest 
hybrids  with  a  pure  and  known  lineage.  The 
original  cross  has  been  repeated  by  Urban,  who 
found  the  hybrid  race  to  be  constant  from  the 
beginning. 

Another  very  notorious  constant  hybrid  race 
is  the  Aegilops  speltaeformis.  It  has  been 
cultivated  in  botanic  gardens  for  more  than 
half  a  century,  mostly  in  annual  or  biennial 
generations.  It  is  sufficiently  fertile  and  al- 
ways comes  true.  Numerous  records  have 
been  made  of  it,  since  formerly  it  was  believed 
by  Fabre  and  others  to  be  a  spontaneous  transi- 
tion from  some  wild  species  of  grass  to  the  ordi- 
nary wheat,  not  a  cross.  Godron,  however, 
showed  that  it  can  be  produced  artificially,  and 
how  it  has  probably  sprung  into  existence 
wherever  it  is  found  wild.  The  hybrid  between 
Aegilops  ovata,  a  small  weed,  and  the  common 
wheat  is  of  itself  sterile,  producing  no  good  pol- 
len. But  it  may  be  fertilized  by  the  pollen  of 
wheat  and  then  gives  rise  to  a  secondary 
hybrid,  which  is  no  other  than  the  Aegilops 
speltaeformis.  This  remained  constant  in  God- 
ron's  experiments  during  a  number  of  genera- 
tions, and  has  been  constant  up  to  the  present 
time. 


266 


Retrograde  Varieties 


Constant  hybrids  have  been  raised  by  Mil- 
lardet  between  several  species  of  strawberries. 
He  combined  the  old  cultivated  forms  with  newly 
discovered  types  from  American  localities. 
They  ordinarily  showed  only  the  characteristics 
of  one  of  their  parents  and  did  not  exhibit  any 
new  combination  of  qualities,  but  they  came 
true  to  this  type  in  the  second  and  later  gener- 
ations. 

In  the  genus  Anemone,  Janczewski  obtained 
the  same  results.  Some  characters  of  course 
may  split,  but  others  remain  constant,  and 
when  only  such  are  present,  hybrid  races  result 
with  new  combinations  of  characters,  which  are 
as  constant  as  the  best  species  of  the  same  ge- 
nus. The  hybrids  of  Janczewski  were  quite  fer- 
tile, and  he  points  out  that  there  is  no  good 
reason  whv  thev  should  not  be  considered  as 
good  new  species.  If  they  had  not  been  pro- 
duced artificially,  but  found  in  the  wild  state, 
their  origin  would  have  been  unknown,  and  there 
can  be  no  doubt  that  they  would  have  been  de- 
scribed by  the  best  systematists  as  species  of  the 
same  value  as  their  parents.  Such  is  especially 
the  case  with  a  hybrid  between  Anemone  magel- 
lanica  and  the  common  Anemone  sylvestris. 

Starting  from  similar  considerations  Kerner 
von  Marilaun  pointed  out  the  fact  long  ago  that 
many    so-called    species,    of    rare    occurrence. 


Unbalanced  Crosses  267 

standing  between  two  allied  types,  may  be  con- 
sidered to  have  originated  by  a  cross.  Surely 
a  wide  field  for  abuse  is  opened  by  such  an  as- 
sertion, and  it  is  quite  a  common  habit  to  con- 
sider intermediate  forms  as  hybrids,  on  the 
grounds  afforded  by  their  external  characters 
alone,  and  without  any  exact  knowledge  of  their 
real  origin  and  often  without  knowing  anything 
as  to  their  constancy  from  seed.  All  such  ap- 
parent explanations  are  now  slowly  becoming 
antiquated  and  obsolete,  but  the  cases  adduced 
by  Kerner  seem  to  stand  this  test. 

Kerner  designates  a  willow,  Salix  ehrliart- 
iana  as  a  constant  hybrid  between  Salix  alba 
and  S,  pentandra.  Rhododendron  intermed- 
ium is  an  intermediate  form  between  the  hairy 
and  the  rusty  species  from  the  Swiss  Alps,  R. 
hirsutum  and  R,  ferrugineum^  the  former  grow- 
ing on  chalky,  and  the  other  on  silicious  soils. 
Wherever  both  these  types  of  soil  occur  in  the 
same  valley  and  these  two  species  approach 
one  another,  the  hybrid  R.  intermedium  is  pro- 
duced, and  is  often  seen  to  be  propagating  itself 
abundantly.  As  is  indicated  by  the  name,  it 
combines  the  essential  characters  of  both  par- 
ents. 

Linaria  italica  is  a  hybrid  toad-flax  between 
L.  genistifolia  and  L.  vulgaris^  a  cross  which  I 
have  repeated  in  my  garden.     Drosera  obovata 


268 


Retrograde  Varieties 


is  a  hybrid  sundew  between  D.  anglica  and  D, 
rotundifolia.  Primula  variabilis  is  a  hybrid 
between  the  two  common  primroses,  P.  offici- 
nalis and  P.  grandiflora.  The  willow-herb 
(Epilobium)j  the  self-heal  (Brunella)  and  the 
yellow  pond-lilies  (Nuphar)  afford  other  in- 
stances of  constant  wild  hybrids. 

Macfarlane  has  discovered  a  natural  hybrid 
between  two  species  of  sundew  in  the  swamps 
near  Atco,  N.  J.  The  parents,  D,  intermedia 
and  D.  filiformis,  were  growing  abundantly  all 
around,  but  of  the  hybrid  only  a  group  of  eleven 
plants  was  found.  A  detailed  comparison  of 
the  hybrid  with  its  parents  demonstrated  a 
minute  blending  of  the  anatomical  peculiarities 
of  the  parental  species. 

Luther  Burbank  of  Santa  Eosa,  California, 
has  produced  a  great  many  hybrid  brambles, 
the  qualities  of  which  in  many  respects  surpass 
those  of  the  wild  species.  Most  of  them  are 
only  propagated  by  cuttings  and  layers,  not 
being  stable  from  seed.  But  some  crosses  be- 
tween the  blackberry  and  the  raspberry  {R. 
fruticosus  and  R.  idaeus)  which  bear  good 
fruit  and  have  become  quite  popular,  are  so 
fixed  in  their  type  as  to  reproduce  their  com- 
posite characters  from  seed  with  as  much  regu- 
larity as  the  species  of  Ruhus  found  in  nature. 
Among  them  are  the  *'  Phenomenal  ''  and  the 


Unbalanced  Crosses  269 

a  Prinius."  The  latter  is  a  cross  between  the 
Californian  dewberry  and  the  Siberian  rasp- 
berry and  is  certainly  to  be  regarded  as  a  good 
stable  species,  artificially  produced.  Bell 
Salter  crossed  the  willow-herbs  Epilobium  tet- 
ragonum  and  E.  montanum,  and  secured  inter- 
mediate hybrids  which  remained  true  to  their 
type  during  four  successive  generations. 

Other  instances  might  be  given.  Many  of 
them  are  to  be  found  in  horticultural  and  bo- 
tanical journals  which  describe  their  system- 
atic and  anatomical  details.  The  question  of 
stability  is  generally  dealt  with  in  an  inci- 
dental manner,  and  in  many  cases  it  is  diffi- 
cult to  reach  conclusions  from  the  facts  given. 
Especially  disturbing  is  the  circumstance  that 
from  a  horticultural  point  of  view  it  is  quite 
sufficient  that  a  new  type  should  repeat  itself  in 
some  of  its  offspring  to  be  called  stable,  and 
that  for  this  reason  absolute  constancy  is  rarely 
proved. 

The  range  of  constant  hybrids  would  be 
larger  by  far  were  it  not  for  two  facts.  The 
first  is  the  absolute  sterility  of  so  many  beauti- 
ful hybrids,  and  the  second  is  the  common  occur- 
rence of  retrogressive  characters  among  culti- 
vated plants.  To  describe  the  importance  of 
both  these  groups  of  facts  would  take  too  much 


270 


Retrograde  Varieties 


time^  and  therefore  it  seems  best  to  give  some 
illustrative  examples  instead. 

Among  the  species  of  Ribes  or  currant,  which 
are  cultivated  in  our  gardens,  the  most  beauti- 
ful are  without  doubt  the  Californian  and  the 
Missouri  currant,  or  Ribes  sanguineum  and  R. 
aureum.  A  third  form,  often  met  with,  is  ^'  Gor- 
don's currant,"  which  is  considered  to  be  a 
hybrid  between  the  two.  It  has  some  peculiar- 
ities of  both  i3arents.  The  leaves  have  the  gen- 
eral form  of  the  Californian  parent,  but  are  as 
smooth  as  the  Missouri  species.  The  racemes 
or  flower-spikes  are  densely  flowered  as  in  the 
red  species,  but  the  flowers  themselves  are  of  a 
yellow  tinge,  with  only  a  flesh-red  hue  on  the 
outer  side  of  the  calyx.  It  grows  vigorously 
and  is  easily  multiplied  by  cuttings,  but  it  never 
bears  any  fruit.  Whether  it  would  be  constant, 
if  fertile,  is  therefore  impossible  to  decide. 

Berheris  ilici folia  is  considered  as  a  hybrid 
between  the  European  barberry  (B.  vulgaris) 
and  the  cultivated  shrub  MaJionia  aqui folia. 
The  latter  has  pinnate  leaves,  the  former  undi- 
vided ones.  The  hybrid  has  undivided  leaves 
which  are  more  spiny  than  those  of  the  Euro- 
pean parent,  and  which  are  not  deciduous  like 
them,  but  persist  during  the  winter,  a  peculiar- 
itv  inherited  from  the  MaJionia.     As  far  as  I 


Unhalanced  Crosses  271 

have  been  able  to  ascertain,  this  hybrid  never 
produces  seed. 

Another  instance  of  an  absolutely  sterile 
hybrid  is  the  often  quoted  Cytisus  adami.  It 
is  a  cross  between  the  common  laburnum 
(Cytisus  Laburnum)  and  another  species  of  the 
same  genus,  C.  purpureus,  and  has  some  traits 
of  both.  But  since  the  number  of  differentiat- 
ing marks  is  very  great  in  this  case,  most  of  the 
organs  have  become  intermediate.  It  is  abso- 
lutely sterile.  But  it  has  the  curious  peculiar- 
ity of  splitting  in  a  vegetative  way.  It  has  been 
multiplied  on  a  large  scale  by  grafting,  and  was 
widely  found  in  the  parks  and  gardens  of 
Europe  during  the  last  century.  Nearly  all 
these  specimens  reverted  from  time  to  time  to 
the  presumable  parents.  Not  rarely  a  bud  of 
Adam's  laburnum  assumed  all  the  qualities  of 
the  common  laburnum,  its  larger  leaves,  richer 
flowered  racemes,  large  and  brightly  yellow 
flowers  and  its  complete  fertility.  Other  buds 
on  the  same  tree  reverted  to  the  purple  parent, 
with  its  solitar}^  small  flowers,  its  dense  shrub- 
like branches  and  very  small  leaves.  These  too 
are  fertile,  though  not  producing  their  seeds  as 
abundantly  as  the  C.  Laburnum  reversions. 
Many  a  botanist  has  sown  the  seeds  of  the  latter 
and  obtained  only  pure  common  C.  Laburnum 
l^lants.     I  had  a  lot  of  nearly  a  hundred  seed- 


272  Retrograde  Varieties 

lings  myself,  many  of  which  have  already  flow- 
ered, bearing  the  leaves  and  flowers  of  the  com- 
mon species.  Seeds  of  the  purple  reversions 
have  also  been  sown,  and  also  yielded  the 
parental  type  only. 

Why  this  most  curious  hybrid  sports  so  reg- 
ularly and  why  others  always  remain  true  to 
their  type  is  as  yet  an  open  question. 

But  recalling  our  former  consideration  of 
this  subject  the  supposition  seems  allowable 
that  the  tendency  to  revert  is  not  connected 
with  the  type  of  the  hybrid,  but  is  apt  to  occur 
in  some  rare  individuals  of  every  type.  But 
since  most  of  the  sterile  hybrids  are  only  known 
to  us  in  a  single  individual  and  its  vegetative 
offspring,  this  surmise  offers  an  explanation  of 
the  rare  occurrence  of  sports. 

Finally,  we  must  consider  some  of  the  so- 
called  hybrid  races  or  strains  of  garden-plants. 
Dahlia,  Gladiolus,  Amaryllis,  Fuchsia,  Pelar- 
gonium and  many  other  common  flowers  afford 
the  best  known  instances.  Immeasurable 
variability  seems  here  to  be  the  result  of 
crossing.  But  on  a  closer  inspection  the  range 
of  characters  is  not  so  very  much  wider  in  these 
hybrid  races  than  in  the  groups  of  parent- 
species  which  have  contributed  to  the  origin  of 
the  hybrids.  Our  tuberous  begonias  owe  their 
variability  to  at  least  seven  original  parent  spe- 


Unbalanced  Crosses  273 

cies,  and  to  the  almost  incredible  number  of 
combinations  which  are  possible  between  their 
characters.  The  first  of  these  crosses  was 
made  in  the  nursery  of  Veitch  and  Sons  near 
London  by  Seden,  and  the  first  hybrid  is  ac- 
cordingly known  as  Begonia  sedeni  and  is  still 
to  be  met  with.  It  has  been  superseded  by  sub- 
sequent crosses  between  the  sedeni  itself  and 
the  veitchi  and  rosiflora,  the  davisii,  the 
clarkii  and  others.  Each  of  them  contributed 
its  advantageous  qualities,  such  as  round  flow- 
ers, rosy  color,  erect  flower  stalks,  elevation  of 
the  flowers  above  the  foliage  and  others.  New 
crosses  are  being  made  continuously,  partly  be- 
tween the  already  existing  hybrids  and  partly 
with  newly  introduced  wild  species.  Only 
rarely  is  it  possible  to  get  pure  seeds,  and  I 
have  not  yet  been  able  to  ascertain  whether  the 
hybrids  would  come  true  from  seed.  Specific 
and  varietal  characters  may  occur  together  in 
many  of  the  several  forms,  but  nothing  is  as 
yet  accurately  known  as  to  their  behavior  in 
pure  fertilizations.  Constancy  and  segregation 
are  thrown  together  in  such  a  manner  that  ex- 
treme variability  results,  and  numerous  beauti- 
ful types  may  be  had,  and  others  may  be  ex- 
pected from  further  crosses.  For  a  scientific 
analysis,  however,  the  large  range  of  recorded 
facts  and  the  written  history,  which  at  first  sight 


274  Retrograde  Varieties 

seems  to  have  no  lacunae,  are  not  sufficient. 
Most  of  the  questions  remain  open  and  need  in- 
vestigation. It  would  be  a  capital  idea  to  try 
to  repeat  the  history  of  the  begonias  or  any 
other  hybrid  race,  making  all  the  described 
crosses  and  then  recording  the  results  in  a  man- 
ner requisite  for  complete  and  careful  scien- 
tific investigations. 

Many  large  genera  of  hybrid  garden-flowers 
owe  their  origin  to  species  rich  in  varieties  or 
in  elementary  subspecies.  Such  is  the  case 
with  the  gladiolus  and  the  tulips.  In  other 
cases  the  original  types  have  not  been  ob- 
tained from  the  wild  state  but  from  the  cultures 
of  other  countries. 

The  dahlias  were  cultivated  in  Mexico  when 
first  discovered  by  Europeans,  and  the  chrys- 
anthemums have  been  introduced  from  the  old 
gardens  of  Japan.  Both  of  them  consisted  of 
various  types,  which  afterwards  have  been  in- 
creased chiefly  by  repeated  intercrossing. 

The  history  of  many  hybrid  races  is  obscure, 
or  recorded  by  different  authorities  in  a  differ- 
ent way.  Some  have  derived  their  evidence 
from  one  nursery,  some  from  another,  and  the 
crosses  evidently  may  have  been  different  in 
different  places.  The  early  history  of  the  glad- 
iolus is  an  instance.  The  first  crosses  are  re- 
corded to  have  been  made  between  Gladiolus 


Unbalanced  Crosses  275 

psittacinus  and  G.  cardinalis,  and  between  their 
hybrid,  which  is  still  known  under  the  name  of 
gandavensis  and  the  purpureo-auratus.  But 
other  authors  give  other  lines  of  descent.  So 
it  is  with  Amaryllis,  which  is  said  by  De  Graaff 
to  owe  its  stripes  to  A.  vittata,  its  fine  form  to 
A.  hrasiliensis,  the  large  petals  to  A.  psittacina, 
the  giant  flowers  to  A.  leopoldi,  and  the  piebald 
patterns  to  A.  pardina.  But  here,  too,  other 
authors  give  other  derivations. 

Summarizing  the  results  of  our  inquiry  we 
see  in  the  first  place  how  very  much  remains  to 
be  done.  Many  old  crosses  must  be  repeated 
and  studied  anew,  taking  care  of  the  purity  of 
the  cross  as  well  as  of  the  harvesting  of  the 
seeds.  Many  supposed  facts  will  be  shown  to 
be  of  doubtful  validity.  New  facts  have  to  be 
gathered,  and  in  doing  so  the  distinction  be- 
tween specific  and  varietal  marks  must  be  taken 
strictly  into  account.  The  first  have  originated 
as  progressive  mutations ;  they  give  unbalanced 
crosses  with  a  constant  offspring,  as  far  as  ex- 
perience now  goes.  The  second  are  chiefly  due 
to  retrograde  modifications,  and  will  be  the  sub- 
ject of  the  next  lecture. 


Lecture  X 

MENDEL  ^S    LAW    OF    BALANCED    CROSSES 

In  the  scientific  study  of  the  result  of  crosses, 
the  most  essential  point  is  the  distinction  of  the 
several  characters  of  the  parents  in  their  combi- 
nation in  the  hybrids  and  their  offspring. 
From  a  theoretical  point  of  view  it  would  be 
best  to  choose  parents  which  would  differ  only 
in  a  single  point.  The  behavior  of  the  differen- 
tiating character  might  then  easily  be  seen. 

Unfortunately,  such  simple  cases  do  not  read- 
ily occur.  Most  species,  and  even  many  ele- 
mentary species  are  distinguished  by  more  than 
one  quality.  Varieties  deviating  only  in  one 
unit-character  from  the  species,  are  more  com- 
mon. But  a  closer  inspection  often  reveals 
some  secondary  characters  which  may  be  over- 
looked in  comparative  or  descriptive  studies, 
but  which  reassume  their  importance  in  experi- 
mental crossings. 

In  a  former  lecture  we  have  dealt  with  the 
qualities  which  must  be  considered  as  being  due 
to  the  acquisition  of  new  characters.    If  we 

276 


Balanced  Crosses  277 

compare  the  new  form  in  this  case  with  the  type 
from  which  it  has  originated,  it  may  be  seen 
that  the  new  character  does  not  find  its  mate, 
or  its  opposite,  and  it  will  be  unpaired  in  the 
hybrid. 

In  the  case  of  retrogressive  changes  the  vis- 
ible modification  is  due,  at  least  in  the  best 
known  instances,  to  the  reduction  of  an  active 
quality  to  a  state  of  inactivity  or  latency.  Now 
if  we  make  a  cross  between  a  species  and  its 
variety,  the  differentiating  character  will  be 
due  to  the  same  internal  unit,  with  no  other 
difference  than  that  it  is  active  in  the  species 
and  latent  in  the  variety.  In  the  hybrid  these 
two  corresponding  units  will  make  a  pair.  But 
while  all  other  pairs  in  the  same  hybrid  indi- 
viduals consist  of  like  antagonists,  only  this 
pair  consists  of  slightly  unlike  opponents. 

This  conception  of  varietal  crosses  leads  to 
three  assertions,  which  seem  justifiable  by 
actual  experience. 

First,  there  is  no  reason  for  a  diminution  of 
the  fertility,  as  all  characters  are  paired  in  the 
hybrid,  and  no  disturbance  whatever  ensues  in 
its  internal  structure.  Secondly,  it  is  quite  in- 
different, how  the  two  types  are  combined,  or 
which  of  them  is  chosen  as  pistillate  and  which 
as  staminate  parent.  The  deviating  pair  will 
have  the  same  constitution  in  both  cases,  being 


278 


Retrograde  Varieties 


built  up  of  one  active  and  one  dormant  unit. 

Thirdly  this  deviating  pair  will  exhibit  the 
active  unit  which  it  contains,  and  the  hybrid 
will  show  the  aspect  of  the  parent  in  which 
the  character  was  active  and  not  that  of  the 
parent  in  which  it  was  dormant.  Now  the  ac- 
tive quality  was  that  of  the  species,  and  its 
latent  state  was  found  in  the  variety.  Hence 
the  inference  that  hybrids  between  a  species 
and  its  retrograde  variety  will  bear  the  aspect 
of  the  species.  This  attribute  may  be  fully 
developed,  and  then  the  hybrid  will  not  be  dis- 
tinguishable from  the  pure  species  in  its  outer 
appearance.  Or  the  character  may  be  incom- 
pletely evolved,  owing  to  the  failure  of  coopera- 
tion of  the  dormant  unit.  In  this  case  the  hy- 
brid will  be  in  some  sense  intermediate  between 
its  parents,  but  these  instances  are  more  rare 
than  the  alternate  ones,  though  presumably 
they  may  play  an  important  part  in  the  varia- 
bility of  many  hybrid  garden-flowers. 

All  of  these  three  rules  are  supported  by  a 
large  amount  of  evidence.  The  complete  fertil- 
ity of  varietal  hybrids  is  so  universally  acknowl- 
edged that  it  is  not  worth  while  to  give  special 
instances.  With  many  prominent  systematists 
it  has  become  a  test  between  species  and  vari- 
eties, and  from  our  present  point  of  view  this  as- 
sumption is  correct.  Only  the  test  is  of  little 
use  in  practice,  as  fertility  may  be  diminished 


Balanced  Crosses  27[) 

in  unbalanced  unions  in  all  possible  degrees,  ao 
cording  to  the  amount  of  difference  between  the 
parents.  If  this  amount  is  slight,  if  for  in- 
stance, only  one  unit-character  causes  the  dif- 
ference, the  injury  to  fertility  may  be  so  small 
as  to  be  practically  nothing.  Hence  we  see  that 
this  test  would  not  enable  us  to  judge  of  the 
doubtful  cases,  although  it  is  quite  sufficient  as 
a  proof  in  cases  of  wider  differences. 

Our  second  assertion  related  to  the  reciprocal 
crosses.  This  is  the  name  given  to  two  sexual 
combinations  between  the  same  parents,  but 
with  interchanged  places  as  to  which  furnishes 
the  pollen.  In  unbalanced  crosses  of  the  genus 
Oenothera  the  hybrids  of  such  reciprocal  unions 
are  often  different,  as  we  have  previously 
shown.  Sometimes  both  resemble  the  pollen- 
parent  more,  in  other  instances  the  pistil-parent. 
In  varietal  crosses  no  such  divergence  is  as  yet 
known.  It  would  be  quite  superfluous  to  ad- 
duce single  cases  as  proofs  for  this  rule,  which 
was  formerly  conceived  to  hold  good  for  hy- 
brids in  general.     The  work  of  the  older  hybrid- 

< 

ists,  such  as  Koelreuter  and  Gaertner  affords 
numerous  instances. 

Our  third  rule  is  of  a  wholly  different  nature. 
Formerly  the  distinction  between  elementary 
species  and  varieties  was  not  insisted  upon,  and 
the  principle  which  stamps  retrograde  changes 


280 


Retrograde  Varieties 


as  the  true  character  of  varieties  is  a  new  one. 
Therefore  it  is  necessary  to  cite  a  considerable 
amount  of  evidence  in  order  to  prove  the  asser- 
tion that  a  hybrid  bears  the  active  character 
of  its  parent-species  and  not  the  inactive  char- 
acter of  the  variety  chosen  for  the  cross. 

We  may  put  this  assertion  in  a  briefer  form, 
stating  that  the  active  character  prevails  in  the 
hybrid  over  its  dormant  antagonist.  Or  as  it 
is  equally  often  put,  the  one  dominates  and  the 
other  is  recessive.  In  this  terminology  the 
character  of  the  species  is  dominant  in  the 
hybrid  while  that  of  the  variety  is  recessive. 
Hence  it  follows  that  in  the  hybrid  the  latent  or 
dormant  unit  is  recessive,  but  it  does  not  follow 
that  these  three  terms  have  the  same  meaning, 
as  we  shall  see  presently.  The  term  recessive 
only  applies  to  the  peculiar  state  into  which  the 
latent  character  has  come  in  the  hybrid  by  its 
pairing  with  the  antagonistic  active  unit. 

In  the  first  place  it  is  of  the  highest  import- 
ance to  consider  crosses  between  varieties  of  re- 
corded origin  and  the  species  from  which  they 
have  sprung.  When  dealing  with  mutations 
of  celandine  we  shall  see  that  the  laciniated 
form  originated  from  the  common  celandine  in 
a  garden  at  Heidelberg  about  the  year  1590. 
Among  my  Oenotheras  one  of  the  eldest  of  the 
recent  productions  is  the  0.  hrevistylis  or  short- 


Balanced  Crosses  281 

styled  species  which  was  seen  for  the  first  time 
in  the  year  1889.  The  third  example  offered 
is  a  hairless  variety  of  the  evening  campion, 
Lychnis  vespertina,  found  the  same  year,  which 
hitherto  had  not  been  observed. 

For  these  three  cases  I  have  made  the  crosses 
of  the  variety  with  the  parent-species,  and  in 
each  case  the  hybrid  was  like  the  species,  and 
not  like  the  variety.  Nor  was  it  intermediate. 
Here  it  is  proved  that  the  older  character  dom- 
inates the  younger  one. 

In  most  cases  of  wild,  and  of  garden-varieties, 
the  relation  between  them  and  the  parent-spe- 
cies rests  upon  comparative  evidence.  Often 
the  variety  is  known  to  be  younger,  in  other 
cases  it  may  be  only  of  local  occurrence,  but 
ordinarily  the  historic  facts  about  its  origin 
have  never  been  known  or  have  long  since  been 
forgotten. 

The  easiest  and  most  widely  known  varietal 
crosses  are  those  between  varieties  with  white 
flowers  and  the  red-  or  blue-flowered  species. 
Here  the  color  prevails  in  the  hybrid  over  the 
lack  of  pigment,  and  as  a  rule  the  hybrid  is  as 
deeply  tinted  as  the  species  itself,  and  cannot  be 
distinguished  from  it,  without  an  investigation 
of  its  hereditary  qualities.  Instances  may  be 
cited  of  the  white  varieties  of  the  snapdragon, 
of  the  red  clover,  the  long-spurred  violet  ( Viola 


282 


Retrograde  Varieties 


cornuta)  the  sea-shore  aster  (Aster  TripoUum), 
corn-rose  (Agrostemma  Githago),  the  Sweet 
William  (Silene  Armeria),  and  many  garden 
flowers,  as  for  instance,  the  Clarkia  pulchella, 
the  Polemofiium  coerulemn,  the  Veronica  longi- 
folia,  the  gloxinias  and  others.  If  the  red  hue 
is  combined  with  a  yellow  ground-color  in  the 
species,  the  variety  will  be  yellow  and  the  hy- 
brid will  have  the  red  and  yellow  mixture  of  the 
species  as  for  instance,  in  the  genus  Geum.  The 
toad-flax  has  an  orange-colored  palate,  and  a 
variety  occurs  in  which  the  palate  is  of  the  same 
yellow  tinge  as  the  remaining  parts  of  the 
corolla.  The  hybrid  between  them  is  in  all  re- 
spects like  the  parent-species. 

Other  instances  could  be  given.  In  berries 
the  same  rule  prevails.  The  black  nightshade 
has  a  variety  with  yellow  berries,  and  the  black 
color  returns  in  the  hybrid.  Even  the  foliage  of 
some  garden-plants  may  afford  instances,  as  for 
instance,  the  purplish  amaranth  (Amaranthus 
caudatus) .  It  has  a  green  variety,  but  the  hy- 
brid between  the  two  has  the  red  foliage  of  the 
species. 

Special  marks  in  leaves  and  in  flowers  follow 
the  same  rule.  Some  varieties  of  the  opium- 
poppy  have  large  black  patches  at  the  basal  end 
of  the  petals,  while  in  others  this  pattern  is  en- 
tirely white.     In  crossing  two  such  varieties, 


Balanced  Crosses  283 

for  instance,  the  dark  "  Mephisto  "  with  the 
white-hearted  ''  Danehrog/'  the  hybrid  shows 
the  active  character  of  the  dark  pattern. 

Hairy  species  crossed  with  their  smooth 
varieties  produce  hairy  hybrids,  as  in  some 
wheats,  in  the  campion  (Lychnis),  in  Biscutella 
and  others.  The  same  holds  good  for  the 
crosses  between  spiny  species  and  their  un- 
armed derivatives,  as  in  the  thorn-apple,  the 
corn-crowfoot  (Ranunculus  arvensis)  and 
others. 

Lack  of  starch  in  seeds  is  observed  in  some 
varieties  of  corn  and  of  peas.  When  such  de- 
rivatives are  crossed  with  ordinary  starch-pro- 
ducing types,  the  starch  prevails  in  the  hybrid. 

It  would  take  too  much  time  to  give  further 
examples.  But  there  is  still  one  point  which 
should  be  insisted  upon.  It  is  not  the  systema- 
tic relation  of  the  two  parents  of  a  cross,  that 
is  decisive,  but  only  the  occurrence  of  the  same 
quality,  in  the  one  in  an  active,  and  in  the  other 
in  an  inactive  condition.  Hence,  whenever  this 
relation  occurs  between  the  parents  of  a  cross, 
the  active  quality  prevails  in  the  hybrid,  even 
when  the  parents  differ  from  each  other  in 
other  respects  so  as  to  be  distinguished  as  sys- 
tematic species.  The  white  and  red  campions 
give  a  red  hybrid,  the  black  and  pale  henbane 
(Hyoscyamus  niger  and  H.  pallidus)  give  a  hy- 


284  Retrograde  Varieties 

brid  with  the  purple  veins  and  center  in  the 
corolla  of  the  former,  the  white  and  blue  thorn- 
apple  produce  a  blue  hybrid,  and  so  on.  In- 
stances of  this  sort  are  common  in  cultivated 
plants. 

Having  given  this  long  list  of  examples  of  the 
rule  of  the  dominancy  of  the  active  character 
over  the  opposite  dormant  unit,  the  question 
naturally  arises  as  to  how  the  antagonistic 
units  are  combined  in  the  hybrid.  This  ques- 
tion is  of  paramount  importance  in  the  consid- 
eration of  the  offspring  of  the  hybrids.  But 
before  taking  it  up  it  is  as  well  to  learn  the  real 
signification  of  recessiveness  in  the  hybrids 
themselves. 

Eecessive  characters  are  shown  by  those  rare 
cases,  in  which  hybrids  revert  to  the  varietal 
parent  in  the  vegetative  way.  In  other  words 
by  bud-variations  or  sports,  analogous  to  the 
splitting  of  Adam's  laburnum  into  its  parents, 
by  means  of  bud-variation  already  described. 
But  here  the  wide  range  of  differentiating  char- 
acters of  the  parents  of  this  most  curious  hybrid 
fail.  The  illustrative  examples  are  extremely 
simple,  and  are  limited  to  the  active  and  inactive 
condition  of  only  one  quality. 

An  instance  is  given  by  the  long-leaved  vero- 
nica {Veronica  longi folia),  which  has  bluish 
flowers  in  long  spikes.     The  hybrid  between 


Balanced  Crosses  285 

this  species  and  its  white  variety  has  a  blue 
corolla.  But  occasionally  it  produces  some 
purely  white  flowers,  showing  its  power  of  sep- 
arating the  parental  heritages,  combined  in  its 
internal  structures.  This  reversion  is  not  com- 
mon, but  in  thousands  of  flowering  spikes  one 
may  expect  to  find  at  least  one  of  them.  Some- 
times it  is  a  whole  stem  springing  from  the 
underground  system  and  bearing  only  white 
flowers  on  all  its  spikes.  In  other  instances  it 
is  only  a  side  branch  which  reverts  and  forms 
white  flowers  on  a  stem,  the  other  spikes  of 
which  remain  bluish.  Sometimes  a  spike  even 
differentiates  longitudinally,  bearing  on  one  side 
blue  and  on  the  other  white  corollas,  and  the 
white  stripe  running  over  the  spike  may  be  seen 
to  be  long  and  large,  or  narrow  and  short  in 
various  degrees.  In  such  cases  it  is  evident 
that  the  heritages  of  the  parents  remain  un- 
influenced by  each  other  during  the  whole  life  of 
the  hybrid,  working  side  by  side,  but  the  active 
element  always  prevails  over  its  latent  opponent 
which  is  ready  to  break  free  whenever  an  oppor- 
tunity is  offered. 

It  is  now  generally  assumed  that  this  incom- 
plete mixture  of  the  parental  qualities  in  a  hy- 
brid, this  uncertain  and  limited  combination  is 
the  true  cause  of  the  many  deviations,  exhibited 
by  varietal  hybrids  when  compared  with  their 


286  Retrograde  Varieties 

parents.  Partial  departures  are  rare  in  the 
hybrids  themselves,  but  in  their  offspring  the 
divergence  becomes  the  rule. 

Segregation  seems  to  be  a  very  difficult  pro- 
cess in  the  vegetative  way,  but  it  must  be  very 
easy  in  sexual  reproduction,  indeed  so  easy  as 
to  show  itself  in  nearly  every  single  instance. 

Leaving  this  first  generation,  the  original 
hybrids,  we  now  come  to  a  discussion  of  their 
offspring.  Hybrids  should  be  fertilized  either 
by  their  own  pollen,  or  by  that  of  other  individ- 
uals born  from  the  same  cross.  Only  in  this 
case  can  the  offspring  be  considered  as  a  means 
of  arriving  at  a  decision  as  to  the  internal  na- 
ture of  the  hybrids  themselves.  Breeders  gen- 
erally prefer  to  fertilize  hybrids  with  the  pollen 
of  their  parents.  But  this  operation  is  to  be 
considered  as  a  new  cross,  and  consequently  is 
wholly  excluded  from  our  present  discussion. 
Hence  it  follows  that  a  clear  insight  into  the 
heredity  of  hybrids  may  be  expected  only  from 
scientific  experiments.  Furthermore  some  of 
the  diversity  observed  as  a  result  of  ordinary 
crosses,  may  be  due  to  the  instability  of  the  par- 
ents themselves  or  at  least  of  one  of  them,  since 
breeders  ordinarily  choose  for  their  crosses 
some  already  very  variable  strain.  Combining 
such  a  strain  with  the  desirable  qualities  of 
some  newly  imported  species,  a  new  strain  may 


Balanced  Crosses  287 

result,  having  the  new  attribute  in  addition  to 
all  the  variability  of  the  old  types.  In  scientific 
experiments  made  for  the  purpose  of  investi- 
gating the  general  laws  of  hybridity,  such  com- 
plex cases  are  therefore  to  be  wholly  excluded. 
The  hereditary  purity  of  the  parents  must  be 
considered  as  one  of  the  first  conditions  of 
success. 

Moreover  the  progeny  must  be  numerous, 
since  neither  constancy,  nor  the  exact  propor- 
tions in  the  case  of  instability,  can  be  deter- 
mined with  a  small  lot  of  plants. 

Finally,  and  in  order  to  come  to  a  definite 
choice  of  research  material,  we  should  keep  in 
mind  that  the  chief  object  is  to  ascertain  the 
relation  of  the  offspring  to  their  parents.  Now 
in  nearly  all  cases  the  seeds  are  separated  from 
the  fruits  and  from  one  another,  before  it  be- 
comes possible  to  judge  of  their  qualities.  One 
may  open  a  fruit  and  count  the  seeds,  but  ordi- 
narily nothing  is  noted  as  to  their  characters. 
In  this  respect  no  other  plant  equals  the  com 
or  maize,  as  the  kernels  remain  together  on  the 
spike,  and  as  it  has  more  than  one  variety 
characterized  by  the  color,  or  constitution,  or 
other  qualities  of  the  grains.  A  corn-grain, 
however,  is  not  a  seed,  but  a  fruit  containing  a 
seed.  Hence  the  outer  parts  pertain  to  the  par- 
ent plant    and  only  the  innermost  ones  to  the 


288  Retrograde  Varieties 

seedling  and  therefore  to  the  following  genera- 
tion. Fruit-characters  thus  do  not  offer  the 
qualities  we  need,  only  the  qualities  resulting 
from  fertilizations  are  characteristic  of  the  new 
generation.  Such  attributes  are  afforded  in 
some  cases  by  the  color,  in  others  by  the  chem- 
ical constitution. 

We  will  choose  the  latter,  and  take  the  sugar- 
corn  in  comparison  with  the  ordinary  or  starch- 
producing  forms  for  our  starting  point.  Both 
sugar-  and  starch-corns  have  smooth  fruits  when 
ripening.  No  difference  is  to  be  seen  in  the 
young  ripe  spikes.  Only  the  taste,  or  a  direct 
chemical  analysis  might  reveal  the  dissimilar- 
ity. But  as  soon  as  the  spikes  are  dried,  a 
diversity  is  apparent.  The  starchy  grains  re- 
main smooth,  but  the  sugary  kernels  lose  so 
much  water  that  they  become  wrinkled.  The 
former  becomes  opaque,  the  latter  more  or  less 
transparent.  Every  single  kernel  may  in- 
stantly be  recognized  as  belonging  to  either  of 
the  types  in  question,  even  if  but  a  single  grain 
of  the  opposite  quality  might  be  met  with  on  a 
spike.  Kernels  can  be  counted  on  the  spike, 
and  since  ordinary  spikes  may  bear  from  300- 
500  grains  and  often  more,  the  numerical  rela- 
tion of  the  different  types  may  be  deduced  with 
great  accuracy. 

Coming  now  to  our  experiment,  both  starchy 


Balanced  Crosses  289 

and  sugary  varieties  are  in  this  respect  wholly 
constant,  when  cultivated  separately.  No 
change  is  to  be  seen  in  the  spikes.  Further- 
more it  is  very  easy  to  make  the  crosses.  The 
best  way  is  to  cultivate  both  types  in  alternate 
rows  and  to  cut  off  the  staminate  panicles  a  few 
days  before  they  open  their  first  flowers.  If 
this  operation  is  done  on  all  the  individuals  of 
one  variety,  sparing  all  the  panicles  of  the 
other,  it  is  manifest  that  all  the  plants  will  be- 
come fertilized  by  the  latter,  and  hence  that  the 
castrated  plants  will  only  bear  hybrid  seeds. 

The  experiment  may  be  made  in  two  ways ;  by 
castrating  the  sugary  or  the  starchy  variety. 
In  both  cases  the  hybrid  kernels  are  the  same. 
As  to  their  composition  they  repeat  the  active 
character  of  the  starchy  variety.  The  sugar  is 
only  accumulated  as  a  result  of  an  incapacity 
of  changing  it  into  starch,  and  the  lack  of  this 
capacity  is  to  be  considered  as  a  retrogressive 
varietal  mark.  The  starch-producing  unit- 
character,  which  is  active  in  the  ordinary  sorts 
of  corns,  is  therefore  latent  in  sugar-corn. 

In  order  to  obtain  the  second  generation,  the 
hybrid  grains  are  sown  under  ordinary  condi- 
tions, but  sufficiently  distant  from  any  other 
variety  of  com  to  insure  pure  fertilization. 
The  several  individuals  may  be  left  to  pollinate 


290  Retrograde  Varieties 

eacli  other,  or  they  may  be  artificially  pollinated 
with  their  own  pollen. 

The  outcome  of  the  experiments  is  shown  by 
the  spikes,  as  soon  as  they  dry.  Each  spike 
bears  two  sorts  of  kernels  irregularly  dispersed 
over  its  surface.  In  this  point  all  the  spikes 
are  alike.  On  each  of  them  one  mav  see  on  the 
first  inspection  that  the  majority  of  the  kernels 
are  starch-containing  seeds,  while  a  minor  part 
becomes  wrinkled  and  transparent  according  to 
the  rule  for  sugary  seeds.  This  fact  shows  at 
once  that  the  hvbrid  race  is  not  stable,  but  has 
differentiated  the  parental  characters,  bringing 
those  of  the  varietal  parent  to  perfect  purity 
and  isolation.  Whether  the  same  holds  good 
for  the  starchy  parent,  it  is  impossible  to  judge 
from  the  inspection  of  the  spikes,  since  it  has 
been  seen  in  the  first  generation  that  the  hybrid 
kernels  are  not  visibly  distinguished  from  those 
of  the  pure  starch-producing  grains. 

It  is  verv  easv  to  count  the  number  of  both 
sorts  of  grains  in  the  spike  of  such  a  hybrid. 
In  doing  so  we  find,  that  the  proportion  is 
nearly  the  same  on  all  the  spikes,  and  only 
slight  variations  would  be  found  in  hundreds 
of  them.  One-fourth  of  the  seeds  are  wrinkled 
and  three-fourths  are  always  smooth.  The 
number  may  vary  in  single  instances  and  be  a 
little  more  or  a  little  less  than  25^,  ranging,  for 


Balanced  Crosses  291 

instance,  from  20  to  27;^ ,  but  as  a  rule,  the  aver- 
age is  found  nearly  equal  to  25^. 

The  sugary  kernels,  when  separated,  from  the 
hybrid  spikes  and  sown  separately,  give  rise  to 
a  pure  sugary  race,  in  no  degree  inferior  in 
purity  to  the  original  variety.  But  the  starchy 
kernels  are  of  different  types,  some  of  them 
being  internally  like  the  hybrids  of  the  first 
generation  and  others  like  the  original  parent. 
To  decide  between  these  two  possibilities,  it  is 
necessary  to  examine  their  progeny. 

For  the  study  of  this  third  hybrid  generation 
we  will  now  take  another  example,  the  opium- 
poppies.  They  usually  have  a  dark  center  in 
the  flowers,  the  inferior  parts  of  the  four  petals 
being  stained  a  deep  purple,  or  often  nearly 
black.  Many  varieties  exhibit  this  mark  as  a 
large  black  cross  in  the  center  of  the  flower.  In 
other  varieties  the  pigment  is  wanting,  the  cross 
being  of  a  pure  white.  Obviously  it  is  only  re- 
duced to  a  latent  condition,  as  in  so  many  other 
cases  of  loss  of  color,  since  it  reappears  in  a 
hybrid  with  the  parent-species. 

For  mv  crosses  I  have  taken  the  dark-centered 
''  Mephisto  "  and  the  ''  Danebrog,"  or  Danish 
flag,  with  a  white  cross  on  a  red  field.  The  sec- 
ond year  the  hybrids  were  all  true  to  the  type  of 
^*  Mephisto."  From  the  seeds  of  each  artifi- 
cially self- fertilized  capsule,  one-fourth  (22.5^^  ) 


292  Retrograde  Varieties 

in  each  instance  reverted  to  the  varietal  mark 
of  the  white  cross,  and  three-fourths  {11. b^) 
retained  the  dark  heart.  Once  more  the  flowers 
were  self-pollinated  and  the  visits  of  insects  ex- 
cluded. The  recessives  now  gave  only  reces- 
sives,  and  hence  we  may  conclude  that  the  varie- 
tal marks  had  returned  to  stability.  The  dark- 
hearted  or  dominants  behaved  in  two  different 
ways.  Some  of  them  remained  true  to  their 
type,  all  their  offspring  being  dark-hearted. 
Evidently  they  had  returned  to  the  parent 
with  the  active  mark,  and  had  reassumed  this 
type  as  purely  as  the  recessives  had  reached 
theirs.  But  others  kept  true  to  the  hybrid  char- 
acter of  the  former  generation,  repeating  in 
their  progeny  exactly  the  same  mixture  as  their 
parents,  the  hybrids  of  the  first  generation,  had 
given. 

This  third  generation  therefore  gives  evi- 
dence, that  the  second  though  apparently  show- 
ing only  two  types,  really  consists  of  three  dif- 
ferent groups.  Two  of  them  have  reassumed 
the  stability  of  their  original  grandparents,  and 
the  third  has  retained  the  instability  of  the  hy- 
brid parents. 

The  question  now  arises  as  to  the  numerical 
relation  of  these  groups.  Our  experiments 
gave  the  following  results : 


Balanced  Crosses 


293 


Cross 


Mephisto 


1.  Generation       2.  (jreneration     3.  Generation 

/4-  100%   Mephisto 


Danebrog 


77.5%  Dom 


All  Mephisto^ 


{ 


9-  all  hybrids  with 
83-68%  domi- 
nants and  17- 
32%   recessives. 


22.5%  Recess. 


100% 
brog. 


Dane 


Examining  these  figures  we  find  one-fourth  of 
constant  recessives,  as  has  already  been  said, 
further  one-fourth  of  constant  dominants,  and 
the  rest  or  one  half  as  unstable  hybrids.  Both 
of  the  pure  groups  have  therefore  reappeared 
in  the  same  numbers.  Calling  A  the  specimens 
with  the  pure  active  mark,  L  those  with  the  la- 
tent mark,  and  H  the  hybrids,  these  proportions 
may  be  expressed  as  follows: 

lA-|-2H-hlL. 

This  simple  law  for  the  constitution  of  the  sec- 
ond generation  of  varietal  hybrids  with  a  single 
differentiating  mark  in  their  parents  is  called 
the  law  of  Mendel.  Mendel  published  it  in 
1865,  but  his  paper  remained  nearly  unknown 
to  scientific  hybridists.  It  is  only  of  late  years 
that  it  has  assumed  a  high  place  in  scientific 
literature,  and  attained  the  first  rank  as  an  in- 
vestigation on  fundamental  questions  of  hered- 


294  Retrograde  Varieties 

ity.  Read  in  the  light  of  modern  ideas  on  unit- 
characters  it  is  now  one  of  the  most  important 
works  on  heredity  and  has  already  widespread 
and  abiding  influence  on  the  philosophy  of  hy- 
bridism in  general. 

But  from  its  very  nature  and  from  the  choice 
of  the  material  made  by  Mendel,  it  is  restricted 
to  balanced  or  varietal  crosses.  It  assumes 
pairs  of  characters  and  calls  the  active  unit  of 
the  pair  dominant,  and  the  latent  recessive, 
without  further  investigations  of  the  question 
of  latency.  It  was  worked  out  by  Mendel  for  a 
large  group  of  varieties  of  peas,  but  it  holds 
good,  with  only  apparent  exceptions,  for  a  wide 
range  of  cases  of  crosses  of  varietal  characters. 
Recently  many  instances  have  been  tested,  and 
even  in  many  cases  third  and  later  generations 
have  been  counted,  and  whenever  the  evidence 
was  complete  enough  to  be  trusted,  Mendel's 
prophecy  has  been  found  to  be  right. 

According  to  this  law  of  Mendel's  the  pairs 
of  antagonistic  characters  in  the  hybrid  split  up 
in  their  progeny,  some  individuals  reverting  to 
the  pure  parental  types,  some  crossing  with 
each  other  anew,  and  so  giving  rise  to  a  new 
generation  of  hybrids.  Mendel  has  given  a 
very  suggestive  and  simple  explanation  of  his 
formula.  Putting  this  in  the  terminology^  of 
to-day,  and  limiting  it  to  the  occurrence  of  only 


Balanced  Crosses  295 

one  differential  unit  in  the  parents,  we  may 
give  it  in  the  following  manner.  In  fertiliza- 
tion, the  characters  of  both  parents  are  not  uni- 
formly mixed,  but  remain  separated  though 
most  intimately  combined  in  the  hybrid 
throughout  life.  They  are  so  combined  as  to 
work  together  nearly  always,  and  to  have  nearly 
equal  influence  on  all  the  processes  of  the  whole 
individual  evolution.  But  when  the  time  ar- 
rives to  produce  progeny,  or  rather  to  produce 
the  sexual  cells  through  the  combination  of 
which  the  offspring  arises,  the  two  parental 
characters  leave  each  other,  and  enter  sepa- 
rately into  the  sexual  cells.  From  this  it  may  be 
seen  that  one-half  of  the  pollen-cells  will  have 
the  quality  of  one  parent,  and  the  other  the  qual- 
ity of  the  other.  And  the  same  holds  good  for 
the  egg-cells.  Obviously  the  qualities  lie  latent 
in  the  pollen  and  in  the  egg,  but  ready  to  be 
evolved  after  fertilization  has  taken  place. 

Granting  these  premises,  we  may  now  ask  as 
to  the  results  of  the  fertilization  of  hybrids, 
when  this  is  brought  about  by  their  own  pollen. 
We  assume  that  numerous  pollen  grains  fer- 
tilize numerous  egg  cells.  This  assumption  at 
once  allows  of  applying  the  law  of  probability, 
and  to  infer  that  of  each  kind  of  pollen  grains 
one-half  will  reach  egg-cells  with  the  same  qual- 


296  Retrograde  Varieties 

ity  and  the  other  half  ovules  with  the  opposite 
character. 

Calling  P  pollen  and  0  ovules,  and  represent- 
ing the  active  mark  by  P  and  0,  the  latent  qual- 
ities by  P'  and  0',  they  would  combine  as  fol- 
lows : 

P  +  O    giving  uniform  pairs  with  the  active  mark, 

P  +  O'  giving  unequal  pairs, 

P'  +  O    giving  unequal  pairs, 

P'  +  O'  giving  uniform  pairs   with   the  latent  mark. 

In  this  combination  the  four  groups  are  ob- 
viously of  the  same  size,  each  containing  one- 
fourth  of  the  offs]3ring.  Manifestly  they  corre- 
spond exactly  to  the  direct  results  of  the 
experiments,  P  -|-  O  representing  the  indi- 
viduals which  reverted  to  the  specific  mark, 
P'-fO'  those  who  reassumed  the  varietal 
quality  and  P+0'  and  P+0'  those  who  hybrid- 
ized for  the  second  time.  These  considerations 
lead  us  to  the  following  form  of  MendePs 
formula  : 

P  -h  O     =  l/4-Active  or  1  A, 

P  4-0') 

P'  +  O  I  "=  1/2-Hybrid  or  2  H, 

P'  +  O'    =l/4-Latent  or  1  L, 

Which  is  evidently  the  same  as  Mendel's 
empirical  law  given  above. 

To  give  the  proof  of  these  assumptions  Men- 
del has  devised  a  very  simple  crossing  experi- 


Balanced  Crosses  297 

ment,  which  he  has  effected  with  his  varieties  of 
peas.  I  have  repeated  it  with  the  sugar-corn, 
which  gives  far  better  material  for  demonstra- 
tion. It  starts  from  the  inference  that  if  dissim- 
ilarity among  the  pollen  grains  is  excluded,  the 
diversity  of  the  ovules  must  at  once  become 
manifest  and  vice  versa.  In  other  terms,  if  a 
hybrid  of  the  first  generation  is  not  allowed  to 
fertilize  itself,  but  is  pollinated  by  one  of  its 
parents,  the  result  will  be  in  accordance  with  the 
Mendelian  formula. 

In  order  to  see  an  effect  on  the  spikes  pro- 
duced in  this  way,  it  is  of  course  necessary  to 
fertilize  them  with  the  pollen  of  the  variety, 
and  not  with  that  of  the  specific  type.  The 
latter  would  give  partly  pure  starchy  grains 
and  partly  hybrid  kernels,  but  these  would 
assume  the  same  type.  But  if  we  pollinate  the 
hybrid  with  pollen  of  a  pure  sugar-corn,  we 
may  predict  the  result  as  follows. 

If  the  spike  of  the  hybrid  contains  dormant 
paternal  marks  in  one-half  of  its  flowers  and  in 
the  other  half  maternal  latent  qualities,  the 
sugar-corn  pollen  will  combine  with  one-half  of 
the  ovules  to  give  hybrids,  and  with  the  other 
half  so  as  to  give  pure  sugar-grains.  Hence 
we  see  that  it  will  be  possible  to  count  out  direct- 
.  ly  the  two  groups  of  ovules  on  inspecting  the 
ripe  and  dry  spikes.     Experience  teaches  us 


298  Retrograde  Varieties 

that  both  are  present,  and  in  nearly  equal  num- 
bers ;  one-half  of  the  grains  remaining  smooth, 
and  the  other  half  becoming  wrinkled. 

The  corresponding  experiment  could  be  made 
with  plants  of  a  pure  sugar-race  by  pollination 
with  hybrid  pollen.  The  spikes  would  show  ex- 
actly tlie  same  mixture  as  in  the  above  case,  but 
now  this  may  be  considered  as  conclusive  proof 
that  half  the  pollen-grains  represent  the  quality 
of  one  parent  and  the  other  half  the  quality  of 
the  other. 

Another  corollary  of  MendePs  law  is  the  fol- 
lowing. In  each  generation  two  groups  return 
to  purity,  and  one-half  remains  hybrid.  These 
last  will  repeat  the  same  phenomenon  of  split- 
ting in  their  progeny,  and  it  is  easily  seen 
that  the  same  rule  will  hold  good  for  all  succeed- 
ing generations.  According  to  Mendel's  prin- 
ciple, in  each  year  there  is  a  new  hybridization, 
differing  in  no  respect  from  the  first  and 
original  one.  If  the  hybrids  only  are  propa- 
gated, each  year  will  show  one-fourth  of  the 
offspring  returning  to  the  specific  character, 
one-fourth  assuming  the  type  of  the  variety  and 
one-half  remaining  hybrid.  T  have  tested  this 
with  a  hybrid  between  the  ordinary  nightshade 
with  black  berries,  and  its  variety,  Solamim 
nigrum  cUorocarpum,  with  pale  yellow  fruits. 

Eight  generations  of  the  hybrids  were  culti- 


Balanced  Crosses  299 

vated,  disregarding  always  the  reverting  off- 
spring. At  the  end  I  counted  the  progeny  of 
the  sixth  and  seventh  generations  and  found 
figures  for  their  three  groups  of  descendants, 
which  exactly  correspond  to  Mendel's  formula. 

Until  now  we  have  limited  ourselves  to  the 
consideration  of  single  differentiating  units. 
This  discussion  gives  a  clear  insight  into  the 
fundamental  phenomena  of  hybrid  fertilization. 
It  at  once  shows  the  correctness  of  the  assump- 
tion of  unit-characters,  and  of  their  pairing  in 
the  sexual  combinations. 

But  MendePs  law  is  not  at  all  restricted  to 
these  simple  cases.  Quite  on  the  contrary,  it 
explains  the  most  intricate  questions  of  hybrid- 
ization, providing  they  do  not  transgress  the 
limits  of  symmetrical  unions.  But  in  this  realm 
nearly  all  results  may  be  calculated  beforehand, 
on  the  ground  of  the  principle  of  probability. 
Only  one  more  assumption  need  be  discussed. 
The  several  pairs  of  antagonistic  characters 
must  be  independent  from,  and  uninfluenced  by, 
one  another.  This  premise  seems  to  hold  good 
in  the  vast  majority  of  cases,  though  rare  excep- 
tions seem  to  be  not  entirely  wanting.  Hence 
the  necessity  of  taking  all  predictions  from  Men- 
del's  law  only  as  probabilities,  which  will  prove 
true  in  most,  but  not  necessarilv  in  all  cases. 


300  Retrograde  Varieties 

But  here   we   will   limit   ourselves   to   normal 
cases. 

The  first  example  to  be  considered  is  obvious- 
ly the  assumption  that  the  parents  of  a  cross 
differ  from  each  other  in  respect  to  two  charac- 
ters. A  good  illustrative  example  is  afforded 
by  the  thorn-apple.  I  have  crossed  the  blue- 
flowered  thorny  form,  usually  known  as  Datura 
Tatula,  with  the  white  thornless  type,  desig- 
nated as  D.  Stramonium  inermis.  Thorns  and 
blue  pigment  are  obviously  active  qualities,  as 
they  are  dominant  in  the  hybrids.  In  the 
second  generation  both  pairs  of  characters  are 
resolved  into  their  constituents  and  paired  anew 
according  to  Mendel  ^s  law.  After  isolating  my 
hybrids  during  the  period  of  flowering,  I  counted 
among  their  progeny : 

128  individuals  with  blue  flowers  and  thorns 
47  "  "        "         "  without       " 

54  "  "     white      "  and       " 

21  "  "        "         "  without       " 


250 

The  significance  of  these  numbers  may  easily 
be  seen,  when  we  calculate  what  was  to  be  ex- 
pected on  the  assumption  that  both  characters 
follow  MendePs  law,  and  that  both  are  inde- 
pendent from  each  other.  Then  we  would  have 
three-fourths  blue  offspring  and  one-fourth  in- 
dividuals with  white  flowers.     Each  of  these 


Balanced  Crosses  301 

two  groups  would  consist  of  thorn-bearing  and 
thornless  plants,  in  the  same  numerical  relation. 
Thus,  we  come  to  the  four  groups  observed  in 
our  experiment,  and  are  able  to  calculate  their 
relative  size  in  the  following  way : 

Proportion 

Blue  with  thorns 3/4X3/4=:  9/16  =  56.25%  9 

Blue,  unarmed 3/4X1/4  =  3/16  =  18.75%  3 

White  with  thorns 1/4X3/4  =  3/16  =  18.75%  3 

White,  unarmed     1/4X1/4=  1/16  =   6.25%  1 

In  order  to  compare  this  inference  from  Men- 
dePs  law  and  the  assumption  of  independency, 
with  the  results  of  our  experiments,  we  must  cal- 
culate the  figures  of  the  latter  in  percentages. 
In  this  way  we  find : 

Found.  Calculated. 

Blue  with  thorns 128  =  51%  56.25% 

Blue  unarmed   47  =  19%  18.75% 

White  with  thorns. .. .       54  =  22%  18.75% 

White  unarmed 21=    8%  6.25% 

The  agreement  of  the  experimental  and  the 
theoretical  figures  is  as  close  as  might  be 
expected. 

This  experiment  is  to  be  considered  only  as 
an  illustrative  example  of  a  rule  of  wide  appli- 
cation. The  rule  obviously  will  hold  good  in 
all  such  cases  as  comply  with  the  two  conditions 
already  premised,  viz.:  that  each  character 
agrees  with  Mendel's  law,  and  that  both  are 
wholly  independent  of  each  other.  It  is 
clear  that  our  figures  show  the  numerical  com- 


302  Retrograde  Varieties 

position  of  the  hybrid  offspring  for  any  single 
instance,  irrespective  of  the  morphological 
nature  of  the  qualities  involved. 

Mendel  has  proved  the  correctness  of  these 
deductions  by  his  experiments  with  peas,  and 
by  combining  their  color  (yellow  or  green)  with 
the  chemical  composition  (starch  or  sugar)  and 
other  pairs  of  characters.  I  will  now  give  two 
further  illustrations  afforded  bv  crosses  of  the 
ordinary  campion.  I  used  the  red-flowered  or 
day-campion,  which  is  a  perennial  herb,  and  a 
smooth  variety"  of  the  white  evening-campion, 
which  flowers  as  a  rule  in  the  first  summer. 
The  combination  of  flower-color  and  pubescence 
gave  the  following  composition  for  the  second 
hybrid  generation: 

Number         %         Calculation 

Hairy  and  red 70  44  56.25% 

Hairy  and  white 23  14  18.75% 

Smooth  and  red 46  23  18.75% 

Smooth  and  white 19  12  6.25% 

For  the  combination  of  pubescence  and  the 
capacity  of  flowering  in  the  first  year  I  found : 

Xumber  %         Calculated 

Hairy,  flowering 286  52  56.25% 

Hairy,  without  stem  .  .    128  23  18.75% 

Smooth,    flowering 96  17  18.75% 

Smooth,  without   stem     42  8  6.25% 

Many  other  cases  have  been  tested  by  dif- 
ferent  writers   and  the   general   result  is   the 


Balanced  Crosses  303 

applicability  of  Mendel's  formula  to  all  cases 
complying  with  the  given  conditions. 

Intentionally  I  have  chosen  for  the  last  ex- 
ample two  pairs  of  antagonisms,  relating  to 
the  same  pair  of  plants,  and  which  may  be 
tested  in  one  experiment  and  combined  in  one 
calculation. 

For  the  latter  we  need  only  assume  the  same 
conditions  as  mentioned  before,  but  now  for 
three  different  qualities.  It  is  easily  seen  that 
the  third  quality  would  split  each  of  our  four 
groups  into  two  smaller  ones  in  the  proportion 

of  3/4 :!/,, 

We  would  then  get  eight  groups  of  the  follow- 
ing composition: 

9/16  X  3/4  =  27/64  or  42.2% 
9/16  X  1/4=  9/64  "  14.1% 


3/16  X  3/4  — 

9/64  " 

14.1% 

3/16  X  1/4 

3/64  " 

4.7% 

3/16  X  3/4 

9/64  " 

14.1% 

3/16  X  1/4 

3/64  " 

4.7% 

1/16  X  3/4 

3/64  " 

4.7% 

1/16  X  1/4 

1/64  '•' 

1.6% 

The  characters  chosen  for  our  experiment  in- 
clude the  absence  of  stem  and  flowers  in  the 
first  year,  and  therefore  would  require  a  second 
year  to  determine  the  flower-color  on  the  per- 
ennial specimens.  Instead  of  doing  so  I  have 
taken  another  character,  shown  by  the  teeth  of 
the  capsules  when  opening.     These  curve  out- 


304  Retrograde  Varieties 

wards  in  the  red  campion,  but  lack  this  capacity 
in  the  evening-campion,  diverging  only  until  an 
upright  position  is  reached.  The  combination 
of  hairs,  colors  and  teeth  gives  eight  groups, 
and  the  counting  of  their  respective  numbers  of 
individuals  gave  the  following  result: 


Teeth 

Hairs 

Flowers 

of  capsules 

Number 

% 

Calculated 

Hairy 

red 

curved 

91 

47 

42.2% 

Hairy 

red 

straight 

15 

7.5 

14.1% 

Hairy 

white 

curved 

23 

12 

14.1% 

Hairy 

white 

straight 

17 

8.5 

4.7% 

Smooth 

red 

curved 

23 

12 

14.1% 

Smooth 

red 

straight 

9 

4.5 

4.7% 

Smooth 

white 

curved 

5 

2.5 

4.7% 

Smooth 

white 

straight 

12 

6 

1.6% 

The  agreement  is  as  comprehensive  as  might 
be  expected  from  an  experiment  with  about  200 
plants,  and  there  can  be  no  doubt  that  a  repeti- 
tion on  a  larger  scale  would  give  still  closer 
agreement. 

In  the  same  way  we  might  proceed  to  crosses 
with  four  or  more  differentiating  characters. 
But  each  new  character  will  double  the  number 
of  the  groups.  Four  characters  will  combine 
into  16  groups,  five  into  32,  six  into  64,  seven 
into  128,  etc.  Hence  it  is  easily  seen  that  the 
size  of  the  experiments  must  be  made  larger 
and  larger  in  the  same  ratio,  if  we  intend  to 
expect    numbers    equally     trustworthy.      For 


Balanced  Crosses  305 

seven  differentiating  marks  16,384  individuals 
are  required  for  a  complete  series.  And  in 
this  set  the  group  with  the  seven  attributes  all 
in  a  latent  condition  would  contain  only  a 
single  individual. 

Unfortunately  the  practical  value  of  these 
calculations  is  not  very  great.  They  indicate 
the  size  of  the  cultures  required  to  get  all  the 
possible  combinations,  and  show  that  in  ordi- 
nary cases  many  thousands  of  individuals  have 
to  be  cultivated,  in  order  to  exhaust  the  whole 
range  of  possibilities.  They  further  show  that 
among  all  these  thousands,  only  very  few  are 
constant  in  all  their  characters ;  in  fact,  it  may 
easily  be  seen  that  with  seven  differentiating 
points  among  the  16,384  named  above,  only  one 
individual  will  have  all  the  seven  qualities  in 
pure  active,  and  only  one  will  have  them  all  in  a 
purely  dormant  condition.  Then  there  will  be 
some  with  some  attributes  active  and  others 
latent,  but  their  numbers  will  also  be  very  small. 
All  others  will  split  up  in  the  succeeding  genera- 
tion in  regard  to  one  or  more  of  their  appar- 
ently active  marks.  And  since  only  in  very 
rare  cases  the  stable  hvbrids  can  be  distin- 
guished  by  external  characters  from  the  un- 
stable ones,  the  stability  of  each  individual 
bearing  a  desired  combination  of  characters 
would  have  to  be  established  by  experiment 


306  Retrograde  Varieties 

after  pure  fertilization.  Menders  law  teaches 
ns  to  predict  the  difficulties,  but  hardly  shows 
any  way  to  avoid  them.  It  lays  great  stress  on 
the  old  prescript  of  isolation  and  pure  fertiliza- 
tion, but  it  will  have  to  be  worked  out  and  ap- 
plied to  a  large  number  of  practical  cases  before 
it  will  gain  a  preeminent  influence  in  horticul- 
tural practice. 

Or,  as  Bailey  states  it,  we  are  only  beginning 
to  find  a  pathway  through  the  bewildering  maze 
of  hybridization. 

This  pathwaj^  is  to  be  laid  out  with  regard  to 
the  following  considerations.  We  are  not  to 
cross  species  or  varieties,  or  even  accidental 
plants.  We  must  cross  unit-characters,  and 
consider  the  plants  only  as  the  bearers  of  these 
units.  We  may  assume  that  these  units  are 
represented  in  the  hereditary  substance  of  the 
cell-nucleus  by  definite  bodies  of  too  small  a  size 
to  be  seen,  but  constituting  together  the  chromo- 
somes. We  may  call  these  innermost  repre- 
sentatives of  the  unit-characters  pangenes,  in 
accordance  with  Darwin's  hypothesis  of  pan- 
genesis, or  give  them  any  other  name,  or  we  may 
even  wholly  abstain  from  such  theoretical  dis- 
cussion, and  limit  ourselves  to  the  conception  of 
the  visible  character-units.  These  units  then 
may  be  present,  or  lacking  and  in  the  first  case 
active,  or  latent. 


Balanced  Crosses  807 

True  elementary  species  differ  from  each 
other  in  a  number  of  unit-characters,  which  do 
not  contrast.  They  have  arisen  by  progressive 
mutation.  One  species  has  one  kind  of  unit, 
another  species  has  another  kind.  On  com- 
bining these,  there  can  be  no  interchange. 
Mendelism  assumes  such  an  interchange  be- 
tween units  of  the  same  character,  but  in  a 
different  condition.  Activity  and  latency  are 
such  conditions,  and  therefore  Mendel's  law 
obviously  applies  to  them.  They  require  pairs 
of  antagonistic  qualities,  and  have  no  connec- 
tion whatever  with  those  qualities  which  do  not 
find  an  opponent  in  the  other  parent.  Now, 
only  pure  varieties  afford  such  pure  conditions. 
When  undergoing  further  modifications,  some 
of  them  may  be  in  the  progressive  line  and 
others  in  the  retrogressive.  Progressive  modi- 
fications give  new  units,  which  are  not  in  con- 
trast with  any  other,  retrograde  changes  turn 
active  units  into  the  latent  condition  and  so  give 
rise  to  pairs.  Ordinary  species  generally 
originate  in  this  way,  and  hence  differ  from 
each  other  partly  in  specific,  partly  in  varietal 
characters.  As  to  the  first,  they  give  in  their 
hybrids  stable  peculiarities,  while  as  to  the 
latter,  they  split  up  according  to  Mendel's  law. 

Unpaired  or  unbalanced  characters  lie  side  by 
side  with  paired  or  balanced  qualities,  and  they 


308  Retrograde  Varieties 

do  so  in  nearly  all  the  crosses  made  for  prac- 
tical purposes,  and  in  very  many  scientific  ex- 
periments. Even  Mendel's  peas  were  not  pure 
in  this  respect,  much  less  do  the  campions  noted 
above  differ  only  in  Mendelian  characters. 

Comparative  and  systematic  studies  must  be 
made  to  ascertain  the  true  nature  of  every  unit 
in  every  single  plant,  and  crossing  experiments 
must  be  based  on  these  distinctions  in  order  to 
decide  what  laws  are  applicable  in  any  case. 


D.    EVER-SPORTING  VARIETIES 

Lecture  XI 

STRIPED   FLOWERS 

Terminology  is  an  awkward  thing.  It  is  as 
disagreeable  to  be  compelled  to  make  new 
names,  as  to  be  constrained  to  use  the  old 
faulty  ones.  Different  readers  may  associate 
different  ideas  with  the  same  terms,  and  unfor- 
tunately this  is  the  case  with  much  of  the 
terminology  of  the  science  of  heredity  and 
variability.  What  are  species  and  what  are 
varieties?  How  many  different  conceptions 
are  conveyed  by  the  terms  constancy  and  varia- 
bility? We  are  compelled  to  use  them,  but  we 
are  not  at  all  sure  that  we  are  rightly  under- 
stood when  we  do  so. 

Gradually  new  terms  arise  and  make  their 
way.  They  have  a  more  limited  applicability 
than  the  old  ones,  and  are  more  narrowly  cir- 
cumscribed. They  are  not  to  supplant  the  older 
terms,  but  permit  their  use  in  a  more  general 
way. 

309 


310  Ever-sporting  Varieties 

One  of  these  doubtful  terms  is  the  word  sport. 
It  often  means  bud-variation,  while  in  other 
cases  it  conveys  the  same  idea  as  the  old  botan- 
ical term  of  mutation.  But  then  all  sorts  of 
seemingly  sudden  variations  are  occasionally 
designated  by  the  same  term  by  one  writer  or 
another,  and  even  accidental  anomalies,  such  as 
teratological  ascidia,  are  often  said  to  arise  by 
sports. 

If  we  compare  all  these  different  conceptions, 
we  will  find  that  their  most  general  feature  is 
the  suddenness  and  the  rarity  of  the  phenom- 
enon. They  convey  the  idea  of  something  un- 
expected, something  not  always  or  not  regularly 
occurring.  But  even  this  demarcation  is  not 
universal,  and  there  are  processes  that  are  reg- 
ularly repeated  and  nevertheless  are  called 
sports.  These  at  least  should  be  designated  by 
another  name. 

In  order  to  avoid  confusion  as  far  as  possible, 
with  the  least  change  in  existing  terminology, 
I  shall  use  the  term  ''  ever-sporting  varieties  " 
for  such  forms  as  are  regularly  propagated  by 
seed,  and  of  pure  and  not  hybrid  origin,  but 
which  sport  in  nearly  every  generation.  The 
term  is  a  new  one,  but  the  facts  are  for  the  most 
part  new,  and  require  to  be  considered  in 
a  new  light.  Its  meaning  will  become  clearer 
at    once    when   the    illustrations    afforded    by 


striped  Flowers  311 

striped  flowers  are  introduced.  In  the  follow- 
ing discussion  it  will  be  found  most  convenient 
to  give  a  summary  of  what  is  known  concerning 
them,  and  follow  this  by  a  consideration  of  the 
detailed  evidence  obtained  experimentally, 
which  supports  the  usage  cited. 

The  striped  variety  of  the  larkspur  of  our 
gardens  is  known  to  produce  monochromatic 
flowers,  in  addition  to  striped  ones.  They  may 
be  borne  by  the  same  racemes,  or  on  different 
branches,  or  some  seedlings  from  the  same 
parent-plant  may  bear  monochromatic  flow- 
ers while  others  may  be  striped.  Such  devia- 
tions are  usually  called  sports.  But  they  occur 
yearly  and  regularly  and  may  be  observed  in- 
variably when  the  cultures  are  large  enough. 
Such  a  variety  I  shall  call  ''  ever-sporting." 

The  striped  larkspur  is  one  of  the  oldest  gar- 
den varieties.  It  has  kept  its  capacity  of 
sporting  through  centuries,  and  therefore  may 
in  some  sense  be  said  to  be  quite  stable.  Its 
changes  are  limited  to  a  rather  narrow  circle, 
and  this  circle  is  as  constant  as  the  peculiari- 
ties of  any  other  constant  species  or  variety. 
But  within  this  circle  it  is  always  changing 
from  small  stripes  to  broad  streaks,  and  from 
them  to  pure  colors.  Here  the  variability  is  a 
thing  of  absolute  constancy,  while  the  constancy 
consists   in   eternal    changes!     Such   apparent 


312  Ever-sporting  Varieties 

contradictions  are  unavoidable,  when  we  ap- 
ply the  old  term  to  such  unusual  though  not 
at  all  new  cases.  Combining  the  stability  and 
the  qualities  of  sports  in  one  word,  we  may  evi- 
dently best  express  it  by  the  new  term  of  ever- 
sporting  variety. 

We  will  now  discuss  the  exact  nature  of  such 
varieties,  and  of  the  laws  of  heredity  which 
govern  them.  But  before  doing  so,  I  might 
point  out,  that  this  new  type  is  a  wery  common 
one.  It  embraces  most  of  the  so-called  variable 
types  in  horticulture,  and  besides  these  a  wide 
range  of  anomalies. 

Every  ever-sporting  variety  has  at  least  two 
different  types,  around  and  between  which  it 
varies  in  numerous  grades,  but  to  which  it  is 
absolutely  limited.  Variegated  leaves  fluctuate 
between  green  and  white,  or  green  and  yellow, 
and  display  these  colors  in  nearly  all  possible 
patterns.  But  there  variability  ends,  and  even 
the  patterns  are  ordinarily  narrowly  prescribed 
in  the  single  varieties.  Double  flowers  afford 
a  similar  instance.  On  one  side  the  single  type, 
on  the  other  the  nearly  wholly  double  model  are 
the  extreme  limits,  between  which  the  variabil- 
ity is  confined.  So  it  is  also  with  monstrosities. 
The  race  consists  of  anomalous  and  normal  in- 
dividuals, and  displays  between  them  all  possi- 
ble   combinations    of    normal    and    monstrous 


striped  Flowers  313 

parts.  But  its  variability  is  restricted  to  this 
group.  And  large  as  the  group  may  seem  on 
first  inspection,  it  is  in  reality  very  narrow. 
Many  monstrosities,  such  as  fasciated  branch- 
es, pitchers,  split  leaves,  peloric  flowers,  and 
others  constitute  such  ever-sporting  varieties, 
repeating  their  anomalies  year  by  year  and  gen- 
eration after  generation,  changing  as  much  as 
possible,  but  remaining  absolutely  true  within 
their  limits  as  long  as  the  variety  exists. 

It  must  be  a  very  curious  combination  of  the 
unit-characters  which  causes  such  a  state  of 
continuous  variability.  The  pure  quality  of  the 
species  must  be  combined  with  the  peculiarity 
of  the  variety  in  such  a  way,  that  the  one  ex- 
cludes the  other,  or  modifies  it  to  some  extent, 
although  both  never  fully  display  themselves 
in  the  same  part  of  the  same  plant.  A  corolla 
cannot  be  at  once  monochromatic  and  striped, 
nor  can  the  same  part  of  a  stem  be  twisted  and 
straight.  But  neighboring  organs  may  show 
the  opposite  attributes  side  by  side. 

In  order  to  look  closer  into  the  real  mechan- 
ism of  this  form  of  variabilitv,  and  of  this  con- 
stant  tendency  to  occasional  reversions,  it  will 
be  best  to  limit  ourselves  first  to  a  single  case, 
and  to  try  to  gather  all  the  evidence,  which 
can  be  obtained  bv  an  examination  of  the  he- 
reditary  relations  of  its  sundry  constituents. 


314:  Ever-sporting  Varieties 

This  may  best  be  done  by  determining  the  de- 
gree of  inheritance  for  the  various  constituents 
of  the  race  during  a  series  of  years.  It  is  only 
necessary  to  apply  the  two  precautions  of  ex- 
cluding all  cross-fertilization,  and  of  gathering 
the  seeds  of  each  individual  separately.  We  do 
not  need  to  ascertain  whether  the  variety  as 
such  is  permanent;  this  is  already  clear  from 
the  simple  fact  of  its  antiquity  in  so  many 
cases.  We  wish  to  learn  what  part  each  in- 
dividual, or  each  group  of  individuals  with 
similar  characters,  play  in  the  common  line 
of  inheritance.  In  other  words,  we  must 
build  up  a  genealogical  tree,  embracing  several 
generations  and  a  complete  set  of  the  single 
cases  occurring  within  the  variety,  in  order  to 
allow  of  its  being  considered  as  a  part  of  the 
genealogy  of  the  whole.  It  should  convey  to  us 
an  idea  of  the  hereditary  relations  during  the 
life-time  of  the  variety. 

It  is  manifest  that  the  construction  of  such 
a  genealogical  tree  requires  a  number  of  sepa- 
rate experiments.  These  should  be  extended 
over  a  series  of  vears.  Each  should  include  a 
number  of  individuals  large  enough  to  allow 
the  determination  of  the  proportion  of  the  dif- 
ferent types  among  the  offspring  of  a  single 
plant.  A  species  which  is  easily  fertilized  by 
its  own  pollen,  and  which  bears  capsules  with 


striped  Flowers  315 

large  quantities  of  seeds,  obviously  affords  the 
best  opportunities.  As  such,  I  have  chosen  the 
common  snapdragon  of  the  gardens,  Antirrhi- 
num majus.  It  has  many  striped  varieties, 
some  tall,  others  of  middle  height,  or  of  dwarfed 
stature.  In  some  the  ground-color  of  the  flow- 
ers is  yellow,  in  others  it  is  white,  the  yellow 
disappearing,  with  the  exception  of  a  large 
mark  in  the  throat.  On  these  ground-colors  the 
red  pigment  is  seen  lying  in  streaks  of  pure  car- 
mine, with  white  intervals  where  the  yellow 
fails,  but  combined  with  yellow  to  make  a  fiery 
red,  and  with  yellow  intervals  when  that  color 
is  present.  This  yellow  color  is  quite  constant 
and  does  not  vary  in  any  marked  degree,  not- 
withstanding the  fact  that  it  seems  to  make 
narrower  and  broader  stripes,  according  to  the 
parts  of  the  corolla  left  free  by  the  red  pig- 
ment. But  it  is  easily  seen  that  this  appearance 
is  only  a  fallacious  one. 

The  variety  of  snapdragon  chosen  was  of  me- 
dium height  and  with  the  yellow  ground-color, 
and  is  known  by  horticulturists  as  A.  majus 
luteum  rubro-striatum.  As  the  yellow  tinge 
showed  itself  to  be  invariable,  I  may  limit  my 
description  to  the  red  stripes. 

Some  flowers  of  this  race  are  striped,  others 
are  not.  On  a  hasty  survey  there  seem  to  be 
three  types,  pure  yellow,  pure  red,  and  stripe? 


316  Ever-sporting  Varieties 

with  all  their  intermediate  links  of  narrower 
and  broader,  fewer  and  more  numerous  streaks. 
But  on  a  close  inspection  one  does  not  succeed 
in  finding  pure  yellow  racemes.  Little  lines  of 
red  may  be  found  on  nearly  every  flower.  They 
are  the  extreme  type  on  this  side  of  the  range 
of  variability.  From  them  an  almost  endless 
range  of  patterns  passes  over  to  the  broadest 
stripes  and  even  to  whole  sections  of  a  pure  red. 
But  then,  between  these  and  the  wholly  red 
flowers  we  observe  a  gap,  which  may  be  narrow- 
er by  the  choice  of  numerous  broad  striped  in- 
dividuals, but  which  is  never  wholly  filled  up. 
Hence  we  see  that  the  red  flowers  are  a  separate 
type  within  the  striped  variety. 

This  red  type  springs  yearly  from  the  striped 
form,  and  yearly  reverts  to  it.  This  is  what  in 
the  usual  descriptions  of  this  snapdragon,  is 
called  its  sporting.  The  breadth  of  the  streaks 
is  considered  to  be  an  ordinary  case  of  varia- 
bility, but  the  red  flowers  appear  suddenly,  with- 
out the  expected  links.  Therefore  they  are  to 
be  considered  as  sports.  Similarly  the  red 
forms  may  suddenly  produce  striped  ones,  and 
this  too  is  to  be  taken  as  a  sport,  according  to 
the  usual  conception  of  the  word. 

Such  sports  may  occur  in  different  ways. 
Either  by  seeds,  or  by  buds,  or  even  within 
the   single   spikes.     Both   opposite   reversions, 


Striped  Flowers  317 

from  striped  to  red  and  from  red  to  stripes,  oc- 
cur by  seed,  even  by  the  strictest  exclusion  of 
cross-fertilization.  As  far  as  my  experiments 
go,  they  are  the  rule,  and  parent-plants  that 
do  not  give  such  reversions,  at  least  in  some  of 
their  offspring,  are  very  rare,  if  not  wholly 
wanting.  Bud-variations  and  variations  within 
the  spike  I  have  as  yet  only  observed  on  the 
striped  individuals,  and  never  on  the  red  ones, 
though  I  am  confident  that  they  might  appear  in 
larger  series  of  experiments.  Both  cases  are 
more  common  on  individuals  with  broad  stripes 
than  on  plants  bearing  only  the  narrower  red 
lines,  as  might  be  expected,  but  even  on  the  al- 
most purely  yellow  individuals  they  may  be  seen 
from  time  to  time.  Bud-variations  produce 
branches  with  spikes  of  uniform  red  flowers. 
Every  bud  of  the  plant  seems  to  have  equal 
chances  to  be  transformed  in  this  way.  Some 
striped  racemes  bear  a  few  red  flowers,  which 
ordinarily  are  inserted  on  one  side  of  the  spike 
only.  As  they  often  cover  a  sharply  defined 
section  of  the  raceme,  this  circumstance  has 
given  rise  to  the  term  of  sectional  variability  to 
cover  such  cases.  Sometimes  the  section  is 
demarcated  on  the  axis  of  the  flower-spike  by  a 
brownish  or  reddish  color,  sharply  contrasting 
with  the  green  hue  of  the  remaining  parts. 
Sectional  variation  mav  be  looked  at  as  a 


318  Ever-sporting  Varieties 

special  type  of  bud-variation,  and  from  this 
point  of  view  we  may  simplify  our  inquiry  and 
limit  ourselves  to  the  inheritance  of  three  types, 
the  striped  plants,  the  red  plants  and  the  red 
asexual  variants  of  the  striped  individuals.  In 
each  case  the  heredity  should  be  observed  not 
only  for  one,  but  at  least  for  two  successive 
generations. 

Leaving  these  introductory  remarks  I  now 
come  at  once  to  the  genealogical  tree,  as  it  may 
be  deduced  from  my  experiments : 


Year. 

1896 
1895 

95%  Str.                              84%  Red 
Striped  Indiv.                         Red  Indiv. 

1895 
1894 

98%  Str.                                 71%  Red. 
Striped  branches.                          Red  branches. 

1894 
1893 

98%  Str.                               76%  Red. 
90%  Striped  Indiv.          10%  Red  Indiv. 

1892 

T 

Striped  Individual. 

This  experiment  was  begun  in  the  year  1892 
with  one  individual  out  of  a  large  lot  of  striped 
plants  grown  from  seeds  which  I  had  purchased 
from  a  firm  in  Erfurt.  The  capsules  were  gath- 
ered separately  from  this  individual  and  about 
40  flowering  plants  were  obtained  from  the 
seeds  in  the  following  year.  Most  of  them  had 
neatly  striped  flowers,  some  displayed  broader 
stripes  and  spare  flowers  were  seen  with  one- 


striped  Flowers  319 

half  wholly  red.  Four  individuals  were  found 
with  only  uniform  red  flowers.  These  were  iso- 
lated and  artificially  pollinated,  and  the  same 
was  done  with  some  of  the  best  striped  indi- 
viduals. The  seeds  from  every  parent  were 
sown  separately,  so  as  to  allow  the  determina- 
tion of  the  proportion  of  uniform  red  individ- 
uals in  the  progeny. 

Neither  group  was  constant  in  its  off- 
spring. But  as  might  be  expected,  the  type 
of  the  parent  plant  prevailed  in  both  groups, 
and  more  strongly  so  in  the  instances  with 
the  striped,  than  with  the  red  ones.  Or,  in 
other  words  seed-reversions  were  more  numer- 
ous among  the  already  reverted  reds  than 
among  the  striped  ij^e  itself.  I  counted  2% 
reversion  in  the  latter  case,  but  24%  from  the 
red  parents. 

Among  the  striped  plants  from  the  striped 
parents,  I  found  some  that  produced  bud- 
variations.  I  succeeded  in  isolating  these  red 
flowering  branches  in  paper  bags  and  in  polli- 
nating them  with  their  own  pollen,  and  subjected 
the  striped  spikes  of  the  same  individuals  to  a 
similar  treatment.  Three  individuals  gave  a 
sufficient  harvest  from  both  types,  and  these 
six  lots  of  seeds  were  sown  separately.  The 
striped  flowers  repeated  their  character  in  98^ 
of  their  offspring,  the  red  twigs  in  only  71^,  the 


320  Ever-sporting  Varieties 

remaining  individuals  sporting  into  the  oppo- 
site group. 

In  the  following  year  I  continued  the  experi- 
ment with  the  seeds  of  the  offspring  of  the  red 
bud-variations.  The  striped  individuals  gave 
95^,  but  in  the  red  ones  only  84^  of  the  progeny 
remained  true  to  the  parent  type. 

From  these  figures  it  is  manifest  that  the 
red  and  striped  types  differ  from  one  another 
not  only  in  their  visible  attributes,  but  also  in 
the  degree  of  their  heredity.  The  striped  in- 
dividuals repeat  their  peculiarity  in  90  -  98^  of 
their  progeny,  2  -  10^  sporting  into  the  uniform 
red  color.  On  the  other  hand  the  red  individ- 
uals are  constant  in  71  -  84^  of  their  offspring, 
while  16-29%  go  over  to  the  striped  type.  Or, 
briefly,  both  types  are  inherited  to  a  high  degree, 
but  the  striped  type  is  more  strictly  inherited 
than  the  red  one. 

Moreover  the  figures  show  that  the  degree  of 
inheritance  is  not  contingent  upon  the  question 
as  to  how  the  sport  may  have  arisen.  Bud- 
sports  show  the  same  degree  of  inheritance  as 
seed-sports.  Sexual  and  asexual  variability 
therefore  seem  to  be  one  and  the  same  process 
in  this  instance.  But  the  deeper  meaning  of 
this  and  other  special  features  of  our  genealog- 
ical tree  are  still  awaiting  further  investigation. 
It  seems  that  much  important  evidence  might 


striped  Flowers  321 

come  from  an  extension  of  this  line  of  work. 
Perhaps  it  might  even  throw  some  light  on 
the  intimate  nature  of  the  bud-variations  of 
ever-sporting  varieties  in  general.  Sectional 
variations  remain  to  be  tested  as  to  the  degree 
of  inheritance  exhibited,  and  the  different  occur- 
rences as  to  the  breadth  of  the  streaks  require 
similar  treatment. 

In  ordinary  horticultural  practice  it  is  desir- 
able to  give  some  guarantee  as  to  what  may  be 
expected  to  come  from  the  seeds  of  brightly 
striped  flowers.  Neither  the  pure  red  type, 
nor  the  nearly  yellow  racemes  are  the  object 
of  the  culture,  as  both  of  them  may  be  had  pure 
from  their  own  separate  varieties.  In  order 
to  insure  proper  striping,  both  extremes  are 
usually  rejected  and  should  be  rooted  out  as 
soon  as  the  flowering  period  begins.  Simi- 
larly the  broad-striped  ones  should  be  re- 
jected, as  they  give  a  too  large  amount  of  uni- 
form red  flowers.  Clearly,  but  not  broadly 
striped  individuals  always  yield  the  most  reli- 
able seed. 

Summing  up  once  more  the  results  of  our  ped- 
igree-experiment, we  may  assert  that  the  striped 
variety  of  the  snapdragon  is  wholly  permanent, 
including  the  two  opposite  types  of  uniform 
color  and  of  stripes.  It  must  have  been  so  since 
it  first  originated  from  the  invariable  uniform 


322  Ever-sporting  Varieties 

varieties,  about  the  middle  of  the  last  century, 
in  the  nursery  of  Messrs.  Vilmorin,  and  prob- 
ably it  will  remain  so  as  long  as  popular  taste 
supports  its  cultivation.  It  has  never  been  ob- 
served to  trangress  its  limits  or  to  sport  into 
varieties  without  reversions  or  sports.  It  fluc- 
tuates from  one  extreme  to  the  other  yearly,  al- 
ways recurring  in  the  following  year,  or  even  in 
the  same  summer  by  single  buds.  Highly  va- 
riable within  its  limits,  it  is  absolutely  constant 
or  permanent,  when  considered  as  a  definite 
group. 

Similar  cases  occur  not  rarely  among  culti- 
vated plants.  In  the  wild  state  they  seem  to 
be  wholly  wanting.  Neither  are  they  met  with 
as  occasional  anomalies  nor  as  distinct  varie- 
ties. On  the  contrary,  many  garden-flowers 
that  are  colored  in  the  species,  and  besides  this 
have  a  white  or  yellow  variety,  have  also 
striped  sorts.  The  oldest  instance  is  probably 
the  marvel  of  Peru,  Mirahilis  Jalappa,  which 
already  had  more  than  one  striped  variety  at 
the  time  of  its  introduction  from  Peru  into  the 
European  gardens,  about  the  beginning  of  the 
seventeenth  century.  Stocks,  liver-leaf  (He- 
patica),  dame's  violet  (Hesperis),  Sweet  Wil- 
liam (Dianthus  harhatus),  and  periwinkles 
{Vinca  minor)  seem  to  be  in  the  same  condition, 
as  their  striped  varieties  were  already  quoted 


striped  Flower's  32 


o 


by  the  writers  of  the  same  century.  Tulips,  hy- 
acinths, Cyclamen,  Azalea,  Camellia,  and  even 
such  types  of  garden-plants  as  the  meadow 
crane's-bill  {Geranium  pratense)  have  striped 
varieties.  It  is  always  the  red  or  blue  color 
which  occurs  in  stripes,  the  underlying  ground 
being  white  or  yellow,  according  to  the  presence 
or  absence  of  the  yellow  in  the  original  color- 
mixture. 

All  these  varieties  are  known  to  be  perma- 
nent, coming  true  during  long  series  of 
successive  generations.  But  very  little  is  known 
concerning  the  more  minute  details  of  their  he- 
reditary qualities.  They  come  from  seed,  when 
this  is  taken  from  striped  individuals,  and 
thence  revert  from  time  to  time  to  the  corre- 
sponding monochromatic  type.  But  whether 
they  would  do  so  when  self-fertilized,  and 
whether  the  reversionary  individuals  are  al- 
ways bound  to  return  towards  the  center  of  the 
group  or  towards  the  opposite  limit,  remains  to 
be  investigated.  Presumably  there  is  nowhere 
a  real  transgression  of  the  limits,  and  never  or 
only  very  rarely  and  at  long  intervals  of  time  a 
true  production  of  another  race  with  other  he- 
reditary qualities. 

In  order  to  satisfy  myself  on  these  points,  I 
made  some  pedigree-cultures  with  the  striped 
forms  of  dame's  violet  (Hesperis  matronalis) 


324  Ever-sporting  Varieties 

and  of  Clarkia  pulchella.  Both  of  them  are 
ever-sporting  varieties.  The  experiments  were 
conducted  during  five  generations  with  the  vi- 
olet, and  during  four  with  the  striped  Clarkia, 
including  the  progeny  of  the  striped  and  of  the 
monochromatic  red  offspring  of  a  primitive 
striped  plant.  I  need  not  give  the  figures  here 
for  the  numerical  relations  between  the  differ- 
ent types  of  each  group,  and  shall  limit  myself 
to  the  statement  that  they  behaved  in  exactly 
the  same  manner  as  the  snapdragon. 

It  is  worth  while  to  dwell  a  moment  on  the 
capacity  of  the  individuals  with  red  flowers  to 
reproduce  the  striped  type  among  their  off- 
spring. For  it  is  manifest  that  this  latter  qual- 
ity must  have  lain  dormant  in  them  during  their 
whole  life.  Darwin  has  already  pointed  out 
that  when  a  character  of  a  grandparent,  which 
is  wanting  in  the  progeny,  reappears  in  the  sec- 
ond generation,  this  quality  must  always  be 
assumed  to  have  been  present  though  latent  in 
the  intermediate  generation.  To  the  many  in- 
stances given  by  him  of  such  alternative  inher- 
itance, the  monochromatic  reversionists  of  the 
striped  varieties  are  to  be  added  as  a  new  type. 
It  is  moreover,  a  very  suggestive  type,  since  the 
latency  is  manifestly  of  quite  another  character 
than  for  instance  in  the  case  of  Mendelian  hv- 

« 

brids,  and  probably  more  allied  to  those  in- 


striped  Flowers  325 

stances,  where  secondary  sexual  marks,  which 
are  as  a  rule  only  evolved  by  one  sex,  are  trans- 
ferred to  the  offspring  through  the  other. 

Stripes  are  by  no  means  limited  to  flowers. 
They  may  affect  the  whole  foliage,  or  the  fruits 
and  the  seeds,  and  even  the  roots.  But  all  such 
cases  occur  much  more  rarely  than  the  striped 
flowers.  An  interesting  instance  of  striped 
roots  is  afforded  by  radishes.  White  and  red 
varieties  of  different  shapes  are  cultivated. 
Besides  them  sometimes  a  curious  motley  sort 
may  be  seen  in  the  markets,  which  is  white  with 
red  spots,  which  are  few  and  narrow  in  some 
samples,  and  more  numerous  and  broader  in 
others.  But  what  is  very  peculiar  and  striking 
is  the  circumstance,  that  these  stripes  do  not 
extend  in  a  longitudinal,  but  in  a  transverse 
direction.  Obviously  this  must  be  the  effect  of 
the  very  notable  growth  in  thickness.  Assum- 
ing that  the  colored  regions  were  small  in 
the  beginning,  they  must  have  been  drawn  out 
during  the  process  of  thickening  of  the  root,  and 
changed  into  transverse  lines.  Rarely  a  streak 
may  have  had  its  greatest  extension  in  a  trans- 
verse direction  from  the  beginning,  in  which 
case  it  would  only  be  broadened  and  not  defi- 
nitely changed  in  its  direction. 

This  variety  being  a  very  fine  one,  and  more 
agreeable  to  the  eye  than  the  uniform  colors,  is 


326  Ever-sporting  Varieties 

being  more  largely  cultivated  in  some  countries. 
It  has  one  great  drawback:  it  never  comes 
wholly  true  from  seed.  It  may  be  grovm  in 
full  isolation,  and  carefully  selected,  all  red  or 
nearly  monochromatic  samples  being  rooted  out 
long  before  blooming,  but  nevertheless  the  seed 
will  always  produce  some  red  roots.  The  most 
careful  selection,  pursued  through  a  number 
of  years,  has  not  been  sufficient  to  get  rid  of 
this  regular  occurrence  of  reversionary  individ- 
uals. Seed-growers  receive  many  complaints 
from  their  clients  on  this  account,  but  they  are 
not  able  to  remove  the  difficulty.  This  experi- 
ence is  in  full  agreement  with  the  experimental 
evidence  given  by  the  snapdragon,  and  it  would 
certainly  be  very  interesting  to  make  a  complete* 
pedigree-culture  with  the  radishes  to  test 
definitely  their  compliance  with  the  rules  ob- 
served for  striped  flowers. 

Horticulturists  in  such  cases  are  in  the  habit 
of  limiting  themselves  to  the  sale  of  so-called 
mixed  seeds.  From  these  no  client  expects  pu- 
rity, and  the  normal  and  hereditary  diversity 
of  types  is  here  in  some  sense  concealed  under 
the  impurities  included  in  the  mixture  from 
lack  of  selection.  Such  cases  invite  scrutiny, 
and  would,  no  doubt,  with  the  methods  of  isola- 
tion, artificial  pollination,  and  the  sowing  of 
the  seeds  separately  from  each  parent,  yield 


striped  Flowers  327 

results  of  great  scientific  value.  Any  one  who 
has  a  garden,  and  sufficient  perseverance  to 
make  pure  cultures  during  a  series  of  years 
might  make  important  contributions  to  scien- 
tific knowledge  in  this  way. 

Choice  might  be  made  from  among  a  wide 
range  of  different  types.  A  variety  of  corn 
called  ^^  Harlequin  ''  shows  stripes  on  its  ker- 
nels, and  one  ear  may  oifer  nearly  white  and 
nearly  red  seeds  and  all  the  possible  interme- 
diate steps  between  them.  From  these  seeds 
the  next  generation  will  repeat  the  motley  ears, 
but  some  specimens  will  produce  ears  of  uniform 
kernels  of  a  dark  purple,  showing  thus  the  or- 
dinary way  of  reversion.  Some  varieties  of 
beans  have  spotted  seeds,  and  among  a  lot  of 
them  one  may  be  sure  to  find  some  purely  red 
ones.  It  remains  to  be  investigated  what  will 
be  their  offspring,  and  whether  they  are  due  to 
partial  or  to  individual  variation. 

The  cockscomb  (Celosia  cristata)  has  varie- 
ties of  nearly  all  colors  from  white  and  yellow 
to  red  and  orange,  and  besides  them  some 
striped  varieties  occur  in  our  gardens,  with  the 
stripes  going  from  the  lower  parts  of  the  stem 
up  to  the  very  crest  of  the  comb.  They  are 
on  sale  as  constant  varieties,  but  nothing  has 
as  yet  been  recorded  concerning  their  peculiar 
behavior    in    the    inheritance    of    the    stripes. 


328  Ever-sporting  Varieties 

Striped  grapes,  apples  and  other  fruits  might 
be  mentioned  in  this  connection. 

Before  leaving  the  striped  varieties,  atten- 
tion is  called  to  an  interesting  deduction,  which 
probably  gives  an  explanation  of  one  of  the 
most  widely  known  instances  of  ever-sporting 
garden  plants.  Striped  races  always  include 
two  types.  Both  of  them  are  fertile,  and  each 
of  them  reproduces  in  its  offspring  both  its 
own  and  the  alternate  type.  It  is  like  a  game 
of  ball,  in  which  the  opposing  parties  always 
return  the  ball.  But  now  suppose  that  only 
one  of  the  types  were  fertile  and  the  other  for 
some  reason  wholly  sterile,  and  assume  the 
reversionary,  or  primitive  monochromatic  indi- 
viduals to  be  fertile,  and  the  derivative  striped 
specimens  to  bloom  without  seed.  If  this  were 
the  case,  knowledge  concerning  the  hereditary 
qualities  would  be  greatly  limited.  In  fact  the 
whole  pedigree  would  be  reduced  to  a  mono- 
chromatic strain,  which  would  in  each  genera- 
tion sport  in  some  individuals  into  the  striped 
variety.  But,  being  sterile,  they  would  not  be 
able  to  propagate  themselves. 

Such  seems  to  be  the  case  with  the  double 
flowered  stocks.  Their  double  flowers  produce 
neither  stamens  nor  pistils,  and  as  each  indi- 
vidual is  either  double  or  single  in  all  its  flow- 
ers, the  doubles  are  wholly  destitute  of  seed. 


striped  Flowers  329 

Nevertheless,  they  are  only  reproduced  by  seed 
frora  single  flowers,  being  an  annual  or  bien- 
nial species. 

Stocks  are  a  large  family,  and  include  a  won- 
derful variety  of  colors,  ranging  from  white 
and  yellow  to  purple  and  red,  and  with  some 
variations  toward  blue.  They  exhibit  also  di- 
versity in  the  habit  of  growth.  Some  are  an- 
nuals, including  the  ten-week  and  pyramidal 
forms ;  others  are  intermediates  and  are  suitable 
for  pot-culture ;  and  the  biennial  sorts  include 
the  well-known  "  Brompton  "  and  '^  Queen  '^ 
varieties.  Some  are  large  and  others  are  small 
or  dwarf.  For  their  brightness,  durability  and 
fragrance,  they  are  deservedly  popular.  There 
are  even  some  striped  varieties.  Horticultur- 
ists and  amateurs  generally  know  that  seed  can 
be  obtained  from  single  stocks  only,  and  that 
the  double  flowers  never  produce  any.  It  is 
not  difficult  to  choose  single  plants  that  will 
produce  a  large  percentage  of  double  blossoms 
in  the  following  generation.  But  only  a  per- 
centage, for  the  experiments  of  the  most  skilled 
growers  have  never  enabled  them  to  save  seed, 
which  would  result  entirely  in  double  flower- 
ing plants.  Each  generation  in  its  turn  is  a 
motley  assembly  of  singles  and  doubles. 

Before  looking  closer  into  the  hereditary  pe- 
culiarities of  this  old  and  interesting  ever  sport- 


330  Ever-a pot  tiny  Varieties 

ing  variety,  it  may  be  as  well  to  give  a  short 
description  of  the  plants  with  double  flowers. 
Generally  speaking  there  are  two  principal 
types  of  doubles.  One  is  by  the  conversion  of 
stamens  into  petals,  and  the  other  is  an  anomaly, 
known  under  the  name  of  petalomany. 

The  change  of  stamens  into  petals  is  a  grad- 
ual modification.  All  intermediate  steps  are 
easily  to  be  found.  In  some  flowers  all  sta- 
mens may  be  enlarged,  in  others  only  part  of 
them.  Often  the  broadened  filaments  bear  one 
or  two  fertile  anthers.  The  fertility  is  no  doubt 
diminished,  but  not  wholly  destroyed.  Individ- 
ual specimens  may  occur,  which  cannot  produce 
any  seed,  but  then  others  of  the  same  lot  may 
be  as  fertile  as  can  be  desired.  As  a  whole, 
such  double  varieties  are  regularly  propagated 
by  seed. 

Petalomany  is  the  tendenc}^  of  the  axis  of 
some  flowers  never  to  make  any  stamens  or  pis- 
tils, not  even  in  altered  or  rudimentary  form. 
Instead  of  these,  they  simply  continue  produc- 
ing petals,  going  on  with  this  production  with- 
out any  other  limit  than  the  supply  of  available 
food.  Numerous  petals  fill  the  entire  space 
within  the  outer  rays,  and  in  the  heart  of  the 
flower  innumerable  young  ones  are  developed 
half-way,  not  obtaining  food  enough  to  attain 


striped  Flowers  331 

full  size.  Absolute  sterility  is  the  natural  con- 
sequence of  this  state  of  things. 

Hence  it  is  impossible  to  have  races  of  petal- 
omanous  types.  If  the  abnormality  happens  to 
show  itself  in  a  species,  which  normally  prop- 
agates itself  in  an  asexual  way,  the  type  may 
become  a  vegetative  variety,  and  be  multiplied 
by  bulbs,  buds  or  cuttings,  etc.  Some  cultivated 
anemones  and  crowfoots  (Ranunculus)  are  of 
this  character,  and  even  the  marsh-marigold 
(Caltha  palustris)  has  a  petalomanous  variety. 
I  once  found  in  a  meadow  such  a  form  of  the 
meadow-buttercup  (Ranunculus  acris),  and  suc- 
ceeded in  keeping  it  in  my  garden  for  several 
years,  but  it  did  not  make  seeds  and  finally 
died.  Camellias  are  known  to  have  both  types 
of  double  flowers.  The  petalomanous  type  is 
highly  regular  in  structure,  so  much  so  as  to  be 
too  uniform  in  all  its  parts  to  be  pleasing,  while 
the  conversion  of  stamens  into  petals  in  the  al- 
ternative varieties  gives  to  these  flowers  a  more 
lively  diversity  of  structure.  Lilies  have  a  va- 
riety called  Lilium  candidum  fore  plena ,  in 
which  the  flowers  seem  to  be  converted  into 
a  long  spike  of  bright,  white  narrow  bracts, 
crowded  on  an  axis  which  never  seems  to  cease 
their  production. 

It  is  manifestly  impossible  to  decide  how  all 
such    sterile   double   flowers   have    originated. 


332  Ever-sporting  Varieties 

Perhaps  each  of  them  originally  had  a  congru- 
ent single-flowered  form,  from  which  it  was  pro- 
duced by  seed  in  the  same  way  as  the  double 
stocks  now  are  yearly.  If  this  assumption  is 
right,  the  corresponding  fertile  line  is  now  lost ; 
it  has  perhaps  died  out,  or  been  masked.  But 
it  is  not  absolutely  impossible  that  such  strains 
might  one  day  be  discovered  for  one  or  another 
of  these  now  sterile  varieties. 

Returning  to  the  stocks  we  are  led  to  the  con- 
ception that  some  varieties  are  absolutely  sin- 
gle, while  others  consist  of  both  single-flowered 
and  double-flowered  individuals.  The  single 
varieties  are  in  respect  to  this  character  true 
to  the  original  wild  type.  They  never  give  seed 
which  results  in  doubles,  providing  all  inter- 
crossing is  excluded.  The  other  varieties  are 
ever-sporting,  in  the  sense  of  this  term  pre- 
viously assumed,  but  with  the  restriction  that 
the  sports  are  exclusively  one-sided,  and  never 
return,  owing  to  their  absolute  sterility. 

The  oldest  double  varieties  of  stocks  have  at- 
tained an  age  of  a  century  and  more.  During 
all  this  time  they  have  had  a  continuous  pedi- 
gree of  fertile  and  single-flowered  individuals, 
throwing  off  in  each  generation  a  definite  num- 
ber of  doubles.  This  ratio  is  not  at  all  depend- 
ent on  chance  or  accident,  nor  is  it  even  variable 
to  a  remarkable  degree.     Quite  on  the  contrary 


striped  Floivers  33 


o 


it  is  always  the  same,  or  nearly  the  same,  and 
it  is  to  be  considered  as  an  inherent  quality  of 
the  race.  If  left  to  themselves,  the  single  indi- 
viduals always  produce  singles  and  doubles  in 
the  same  quantity ;  if  cultivated  after  some  spe- 
cial method,  the  proportion  may  be  slightly 
changed,  bringing  the  proportion  of  doubles 
up  to  60;^  or  even  more. 

Ordinarily  the  single  and  double  members  of 
such  a  race  are  quite  equal  in  the  remainder  of 
their  attributes,  especially  in  the  color  of  their 
flowers.    But  this  is  not  always  the  case.    The 
colors  of  such  a  race  may  repeat  for  themselves 
the  peculiarities  of  the  ever-sporting  characters. 
It  often  happens  that  one  color  is  more  or  less 
strictly  allied  to  the  doubles,  and  another  to 
the  singles.     This  sometimes  makes  it  difficult 
to  keep  the  various  colors  true.     There  are  cer- 
tain sorts,  which  invariably  exhibit  a  difference 
in  color  between  the  single  and  the  double  flow- 
ers.    The  sulphur-yellow  varieties  may  be  ad- 
duced as  illustrative  examples,  because  in  them 
the  single  flowers  always  come  white.     Hence  in 
saving  seed,  it  is  impossible  so  to  select  the 
plant,  that  an  occasional  white  does  not  also 
appear  among  the  double  flowers,  agreeing  in 
this  deviation  with  the  general  rule  of  the  ever- 
sporting  varieties. 

I  commend  all  the  above  instancoR  to  those 


334  Ever-sporting  Varieties 

who  wish  to  make  pedigree-cultures.  The  co- 
operation of  many  is  needed  to  bring  about  any 
notable  advancement,  since  the  best  way  to  se- 
cure isolation  is  to  restrict  one's  self  to  the 
culture  of  one  strain,  so  as  to  avoid  the  inter- 
mixture of  others.  So  many  facts  remain  doubt- 
ful and  open  to  investigation,  that  almost  any 
lot  of  purchased  seed  may  become  the  starting- 
point  for  interesting  researches.  Among  these 
the  sulphur-yellow  varieties  should  be  consid- 
ered in  the  first  place. 

In  respect  to  the  great  questions  of  heredity, 
the  stocks  offer  many  points  of  interest.  Some 
of  these  features  I  will  now  trv  to  describe,  in 
order  to  show  what  still  remains  to  be  done, 
and  in  what  manner  tlie  stocks  mav  clear  the 
way  for  the  study  of  the  ever-sporting  varieties. 

The  first  point,  is  the  question,  which  seeds 
become  double-flowered  and  which  single-flow- 
ered plants!  Beyond  all  doubt,  the  determi- 
nation has  taken  place  before  the  ripening  of  the 
seed.  But  though  the  color  of  the  seed  is  often 
indicative  of  the  color  of  the  flowers,  as  in  some 
red  or  purple  varieties,  and  though  in  balsams 
and  some  other  instances  the  most  ^^  highly 
doubled  "  flowers  are  to  be  obtained  from  the 
biggest  and  plumpest  seeds,  no  such  rule  seems 
to  exist  respecting  the  double  stocks.  Now 
if   one  half  of  the   seeds   gives   doubles,    and 


striped  Floivers  335 

the  other  half  singles,  the  question  arises, 
where  are  the  singles  and  the  doubles  to  be 
found  on  the  parent-plant? 

The  answer  is  partly  given  by  the  following 
experiment.  Starting  from  the  general  rule  of 
the  great  influence  of  nutrition  on  variability, 
it  may  be  assumed  that  those  seeds  will  give 
most  doubles,  that  are  best  fed.  Now  it  is  man- 
ifest that  the  stem  and  larger  branches  are  in 
a  better  condition  than  the  smaller  twigs,  and 
that  likewise  the  first  fruits  have  better  chances 
than  the  ones  formed  later.  Even  in  the  same 
pod  the  uppermost  seeds  will  be  in  a  compara- 
tively disadvantageous  position.  This  concep- 
tion leads  to  an  experiment  which  is  the  basis 
of  a  practical  method  much  used  in  France  in 
order  to  get  a  higher  percentage  of  seeds  of 
double-flowering  plants. 

This  method  consists  in  cutting  off,  in  the  first 
place  the  upper  parts  of  all  the  larger  spikes,  in 
the  second  place,  the  upper  third  part  of  each 
pod,  and  lastly  all  the  small  and  weak  twigs. 
In  doing  so  the  percentage  is  claimed  to  go  up 
to  67  -  70^,  and  in  some  instances  even  higher. 
This  operation  is  to  be  performed  as  soon  as  the 
required  number  of  flowers  have  ceased  blos- 
soming. All  the  nutrient  materials,  destined 
for  the  seeds,  are  now  forced  to  flow  into  these 
relativelv   few   embrvos,   and   it   is   clear  that 


336  Ever-sporting  Varieties 

they  will  be  far  better  nourished  than  if  no 
operation  were  made. 

In  order  to  control  this  experiment  some 
breeders  have  made  the  operation  on  the  fruits 
when  ripe,  instead  of  on  the  young  pods,  and 
have  saved  the  seeds  from  the  upper  parts  sep- 
arately. This  seed,  produced  in  abundance, 
was  found  to  be  very  poor  in  double  flowers, 
containing  only  some  20-30^.  On  the  con- 
trary the  percentage  of  doubles  in  the  seed  of 
the  lower  parts  was  somewhat  augmented,  and 
the  average  of  both  would  have  given  the  normal 
proportion  of  50%. 

Opposed  to  the  French  method  is  the  German 
practice  of  cultivating  stocks,  as  I  have  seen  it 
used  on  a  very  large  scale  at  Erfurt  and  at  other 
places.  The  stocks  are  grown  in  pots  on  small 
scaffolds,  and  not  put  on  or  into  the  earth. 
The  obvious  aim  of  this  practice  is  to  keep  the 
earth  in  the  pots  dry,  and  accordingly  they  are 
only  scantily  watered.  In  consequence  they 
cannot  develop  as  fully  as  they  would  have  done 
when  planted  directly  in  the  beds,  and  they  pro- 
duce only  small  racemes  and  no  weak  twigs, 
eliminating  thereb}^  without  further  operation 
the  weaker  seeds  as  by  the  French  method. 
The  effect  is  increased  by  planting  from  6-10 
separate  plants  in  each  pot. 

It  would  be  very  interesting  to  make  compar- 


Striped  Flowers  337 

ative  trials  of  both  methods,  in  order  to  discover 
the  true  relation  between  the  practice  and  the 
results  reached.  Both  should  also  be  compared 
with  cultures  on  open  plots,  which  are  said  to 
give  only  50;j^  of  doubles.  This  last  method  of 
culture  is  practiced  wherever  it  is  desired  to 
produce  great  quantities  of  seeds  at  a  low  cost. 
Such  trials  would  no  doubt  give  an  insight  into 
the  relations  of  hereditary  characters  to  the 
distribution  of  the  food  within  the  plant. 

A  second  point  is  the  proportional  increase  of 
the  double-flowering  seeds  with  age.  If  seed 
is  kept  for  two  or  three  years,  the  greater  part 
of  the  grains  will  gradually  die,  and  among  the 
remainder  there  is  found  on  sowing,  a  higher 
percentage  of  double  ones.  Hence  we  may  in- 
fer that  the  single-flowered  seeds  are  shorter- 
lived  than  the  doubles,  and  this  obviously  points 
to  a  greater  weakness  of  the  first.  It  is  quite 
evident  that  there  is  some  common  cause  for 
these  facts  and  for  the  above  cited  experience, 
that  the  first  and  best  pods  give  more  doubles. 
Much,  however,  remains  to  be  investigated  be- 
fore a  satisfactory  answer  can  be  made  to  these 
questions. 

A  third  point  is  the  curious  practice,  called 
b}^  the  French  ^^  esimpler,"  and  which  consists 
in  pulling  out  the  singles  when  very  young.  It 
seems  to  be  done  at  an  age  when  the  flower-buds 


338  Ever-sporting  Varieties 

are  not  yet  visible,  or  at  least  are  not  far 
enough  developed  to  show  the  real  distinctive 
marks.  Children  may  be  employed  to  choose 
and  destroy  the  singles.  There  are  some  slight 
differences  in  the  fullness  and  roundness  of  the 
buds  and  the  pubescence  of  the  young  leaves. 
Moreover  the  buds  of  the  doubles  are  said  to 
be  sweeter  to  the  taste  than  those  of  the  singles. 
But  as  yet  I  have  not  been  able  to  ascertain, 
whether  any  scientific  investigation  of  this  proc- 
ess has  ever  been  made,  though  according  to 
some  communications  made  to  me  bv  the  late 
Mr.  Cornu,  the  practice  seems  to  be  very  gen- 
eral in  the  environs  of  Paris.  In  summer  large 
fields  may  be  seen,  bearing  exclusively  double 
flowers,  owing  to  the  weeding  out  of  the  singles 
long  before  flowering. 

Bud- variation  is  the  last  point  to  be  taken  up. 
It  seems  to  be  verv  rare  with  stocks,  but  some 
instances  have  been  recorded  in  literature. 
Darwin  mentions  a  double  stock  with  a  branch 
bearing  single  flowers,  and  other  cases  are 
known  to  have  occurred.  But  in  no  instance 
does  the  seed  of  such  a  bud-variant  seem  to 
have  been  saved.  Occasionally  other  rever- 
sions also  occur.  From  time  to  time  speci- 
mens appear  with  more  luxurious  growth 
and  with  divergent  instead  of  erect  pods. 
They  are  called,  in  Erfurt,  ^'  generals  "  on  ac- 


striped  Flowers  339 

count  of  their  stiff  and  erect  appearance, 
and  they  are  marked  by  more  divergent  horns 
crowning  the  pods.  They  are  said  to  produce 
only  a  relatively  small  number  of  doubles  from 
their  seeds,  and  even  this  small  number  might 
be  due  to  fertilization  with  pollen  of  their 
neighbors.  I  saw  some  of  these  reversionary 
types,  when  inspecting  the  nurseries  of  Erfurt, 
but  as  they  are,  as  a  rule,  thrown  out  before 
ripening  their  seed,  nothing  is  exactly  known 
about  their  real  hereditary  qualities. 

Much  remains  to  be  cleared  up,  but  it  seems 
that  one  of  the  best  means  to  find  a  way  through 
the  bewildering  maze  of  the  phenomena  of  in- 
heritance, is  to  make  groups  of  related  forms 
and  to  draw  conclusions  from  a  comparison  of 
the  members  of  such  groups.  Such  comparisons 
must  obviously  give  rise  to  questions,  which  in 
their  turn  will  directly  lead  to  experimental  in- 
vestigation. 


Lecture  XII 


FIVE-LEAVED  CLOVER 


Every  one  knows  the  ^'  four-leaved  "  clover. 
It  is  occasionally  found  on  lawns,  in  pastures 
and  by  the  roadsides.  Specimens  with  five  leaf- 
lets may  be  found  now  and  then  in  the  same 
place,  or  on  the  same  plant,  but  these  are  rarer. 
I  have  often  seen  isolated  plants  with  quater- 
nate  leaves,  but  only  rarely  have  I  observed  in- 
dividuals with  more  than  one  such  leaf. 

The  two  cases  are  essentially  dissimilar. 
They  may  appear  to  differ  but  little  morpholog- 
ically, but  from  the  point  of  view  of  heredity 
they  are  quite  different.  Isolated  quaternate 
leaves  are  of  but  little  interest,  while  the  occur- 
rence of  many  on  the  same  individual  indicates  a 
distinct  variety.  In  making  experiments  upon 
this  point  it  is  necessary  to  transplant  the  di- 
vergent individuals  to  a  garden  in  order  to 
furnish  them  proper  cultural  conditions  and 
to  keep  them  under  constant  observation.  When 
a  plant  bearing  a  quaternate  leaf  is  thus 
transplanted   however,    it    rarely    repeats    the 

340 


Five-leaved  Clover  341 

anomaly.  But  when  plants  with  two  or  more 
quaternate  leaves  on  the  same  individual  are 
chosen  it  indicates  that  it  belongs  to  a  definite 
race,  which  under  suitable  conditions  may 
prove  to  become  very  rich  in  the  anomalies  in 
question. 

Obviously  it  is  not  always  easy  to  decide 
definitely  whether  a  given  individual  belongs  to 
such  a  race  or  not.  Many  trials  may  be  neces- 
sary to  secure  the  special  race.  I  had  the  good 
fortune  to  find  two  plants  of  clover,  bearing  one 
quinate  and  several  quaternate  leaves,  on  an 
excursion  in  the  neighborhood  of  Loosdrecht  in 
Holland.  After  transplanting  them  into  my 
garden,  I  cultivated  them  during  three  years 
and  observed  a  slowly  increasing  number  of 
anomalous  leaves.  This  number  in  one  summer 
amounted  to  46  quaternate  and  16  quinate 
leaves,  and  it  was  evident  that  I  had  secured  an 
instance  of  the  rare  ^'  five-leaved  "  race  which 
I  am  about  to  describe. 

Before  doing  so  it  seems  desirable  to  look 
somewhat  closer  into  the  morphological  fea- 
tures of  the  problem.  Pinnate  and  palmate 
leaves  often  vary  in  the  number  of  their  parts. 
This  variability  is  generally  of  the  nature  of  a 
common  fluctuation,  the  deviations  grouping 
themselves  around  an  average  type  in  the  ordi- 
nary way.     Ash   leaves   bear   ^lyq   pairs,   and 


342  Ever-sporting  Varieties 

the  mountain-ash  (Sorbus  Aucuparia)  has  six 
pairs  of  leaflets  in  addition  to  the  terminal  one. 
But  this  number  varies  slightly,  the  weaker 
leaves  having  less,  the  stronger  more  pairs  than 
the  average.  Such  however,  is  not  the  case 
with  ternate  leaves,  which  seem  to  be  quite  con- 
stant. Four  leaflets  occur  so  very  rarely  that 
one  seems  justified  in  regarding  them  rather  as 
an  anomaly  than  as  a  fluctuation.  And  this  is 
confirmed  by  the  almost  universal  absence  of 
two-bladed  clover-leaves. 

Considering  the  deviation  as  an  anomaly,  we 
may  look  into  its  nature.  Such  an  inquiry 
shows  that  the  supernumerary  leaflets  owe  their 
origin  to  a  splitting  of  one  or  more  of  the  nor- 
mal ones.  This  splitting  is  not  terminal,  as  is 
often  the  case  with  other  species,  and  as  it  may 
be  seen  sometimes  in  the  clover.  It  is  for 
the  most  part  lateral.  One  of  the  lateral  nerves 
grows  out  becoming  a  median  nerve  of  the  new 
leaflet.  Intermediate  steps  are  not  wanting, 
though  rare,  and  they  show  a  gradual  separa- 
tion of  some  lateral  part  of  a  leaflet,  until  this 
division  reaches  the  base  and  divides  the  leaflet 
into  two  almost  equal  parts.  If  this  splitting 
occurs  in  one  leaflet  we  get  the  *^  four-leaved  " 
clover,  if  it  occurs  in  two  there  will  be  five  leaf- 
lets. And  if,  besides  this,  the  terminal  leaflet 
produces  a  derivative  on  one  or  both  of  its  sides, 


Five-leaved  Clover  343 

we  obtain  a  crown  of  six  or  seven  leaflets  on  one 
stalk.  Such  were  often  met  with  in  the  race  I 
had  under  cultivation,  but  as  a  rule  it  did  not  ex- 
ceed this  limit. 

The  same  phenomenon  of  a  lateral  doubling 
of  leaflets  may  of  course  be  met  with  in  other 
instances.  The  common  laburnum  has  a  va- 
riety which  often  produces  quaternate  and 
quinate  leaves,  and  in  strawberries  I  have  also 
seen  instances  of  this  abnormality.  It  occurs 
also  in  pinnate  leaves,  and  complete  sets  of  all 
the  intermediate  links  may  often  be  found  on 
the  false  or  bastard-acacia  (Robinia  Pseud- 
Acacia). 

Opposed  to  this  increase  of  the  number  of 
leaflets,  and  still  more  rare  and  more  curious  is 
the  occurrence  of  ^^  single-leaved  ''  varieties 
among  trees  and  herbs  with  pinnate  or  temate 
leaves.  Only  very  few  instances  have  been  de- 
scribed, and  are  cultivated  in  gardens.  The 
ashes  and  the  bastard-acacia  may  be  quoted 
among  trees,  and  the  ^^  one-leaved  "  strawberry 
among  herbs.  Here  it  seems  that  several  leaf- 
lets have  been  combined  into  one,  since  this  one 
is,  as  a  rule,  much  larger  than  the  terminal  leaf- 
let of  an  ordinary  Teaf  of  the  same  species. 
These  monophyllous  varieties  are  interesting 
also  on  account  of  their  continuous  but  often  in- 
complete reversion  to  the  normal  type. 


344  Ever-sporting  Varieties 

Pinnate  and  palmate  leaves  are  no  doubt 
derivative  types.  They  must  have  originated 
from  the  ordinary  simple  leaf.  The  monophyl- 
ly  may  therefore  be  considered  as  a  reversion  to 
a  more  primitive  state  and  the  monophyllous 
varieties  may  be  called  atavistic. 

On  the  other  hand  we  have  seen  that  these 
atavistic  varieties  may  revert  to  their  nearest 
progenitors,  and  this  leads  to  the  curious  con- 
ception of  positive  and  negative  atavism.  For 
if  the  change  of  compound  leaves  into  single 
ones  is  a  retrograde  or  negative  step,  the  con- 
version of  single  or  ternate  leaves  into  pinnate 
and  palmate  ones  must  evidently  be  considered 
in  this  case  as  positive  atavism. 

This  discussion  seems  to  throw  some  light  on 
the  increase  of  leaflets  in  the  clover.  The  pea- 
family,  or  the  group  of  papilionaceous  plants, 
has  pinnate  leaves  ordinarily,  which,  according 
to  our  premises,  must  be  considered  as  a  deriva- 
tive type.  In  the  clovers  and  their  allies  this 
type  reverts  halfway  to  the  single  form,  pro- 
ducing only  three  leaflets  on  each  stalk.  If  now 
the  clover  increases  its  number  of  leaflets,  this 
may  be  considered  as  a  reversion  to  its  nearest 
progenitors,  the  papilionaceous  plants  with  pin- 
nate leaves.  Hence  a  halfway  returning  and 
therefore  positive  atavism.  And  as  I  have  al- 
ready mentioned  in  a  former  lecture,  pinnate 


Five-leaved  Clover  345 

leaves  are  also  sometimes  produced  by  my  new 
race  of  clover. 

Returning  to  the  original  plants  of  this  race, 
it  is  evidently  impossible  to  decide  whether  they 
were  really  the  beginning  of  a  new  strain,  and 
had  originated  themselves  by  some  sudden 
change  from  the  common  type,  or  whether 
they  belonged  to  an  old  variety,  which  had 
propagated  itself  perhaps  during  centuries, 
unobserved  by  man.  But  the  same  diffi- 
culty generally  arises  when  new  varieties  are 
discovered.  Even  the  behavior  of  the  plants 
themselves  or  of  their  progeny  does  not  afford 
any  means  of  deciding  the  question.  The  sim- 
plest way  of  stating  the  matter  therefore,  is  to 
say  that  I  accidentally  found  two  individuals  of 
the  ^  ^  five-leaved ' '  race.  By  transplanting  them 
into  my  garden,  I  have  isolated  them  and  kept 
them  free  from  cross-fertilization  with  the  ordi- 
nary type.  Moreover,  I  have  brought  them  un- 
der such  conditions  as  are  necessary  for  the  full 
development  of  their  characters.  And  last  but 
not  least,  I  have  tried  to  improve  this  character 
as  far  as  possible  by  a  very  rigid  and  careful 
selection. 

The  result  of  all  this  effort  has  been  a  rapid 
improvement  of  my  strain.  I  saved  the  seed 
of  the  original  plants  in  1889  and  cultivated  the 
second   generation  in  the  following  year.     It 


346  Ever-sporting  Varieties 

showed  some  increase  of  the  anomaly,  but  not  to 
a  very  remarkable  degree.  In  the  flowering  pe- 
riod I  selected  four  plants  with  the  largest  num- 
ber of  quaternate  and  quinate  leaves  and  de- 
stroyed all  the  others.  I  counted  in  the  average 
25  anomalous  organs  on  each  of  them.  From 
their  seed  I  raised  the  third  generation  of  my 
culture  in  the  year  1891. 

This  generation  included  some  300  plants,  on 
which  above  8000  leaves  were  counted.  More 
than  1000  were  quaternate  or  quinate,  the  ter- 
nate  leaves  being  still  in  the  majority.  But  the 
experiment  clearly  showed  that '  ^  four-leaved  ' ' 
clovers  may  be  produced  in  any  desired  quan- 
tity, provided  that  the  seed  of  the  variety  is 
available.  In  the  summer  only  three,  four  and 
five  leaflets  on  one  stalk  were  seen,  but  towards 
the  fall,  and  after  the  selection  of  the  best  in- 
dividuals, this  number  increased  and  came  up 
to  six  and  seven  in  some  rare  instances. 

The  selection  in  this  year  was  by  no  means 
easy.  Nearly  all  the  individuals  produced  at 
least  some  quaternate  leaves,  and  thereby 
showed  the  variety  to  be  quite  pure.  I  counted 
the  abnormal  organs  on  a  large  group  of  the 
best  plants,  and  selected  20  excellent  speci- 
mens from  them,  with  more  than  one-third  of 
all  their  leaves  changed  in  the  desired  manner. 

Having  brought  my  race  up  to  this  point,  I 


Five-leaved  Clover  347 

was  able  to  introduce  a  new  and  far  more  easy- 
mark,  afforded  by  the  seedlings,  for  my  selec- 
tions. This  mark  has  since  remained  constant, 
and  has  brought  about  a  rapid  continuance  of 
the  improvement,  without  necessitating  such 
large  cultures. 

This  seedling  in  the  various  species  of 
clover  usually  begins  with  a  first  leaf  above 
the  cotyledons  of  a  different  structure  from 
those  that  follow.  It  has  only  one  blade 
instead  of  three.  But  in  my  variety  the  in- 
crease of  the  number  of  the  leaflets  may  extend 
to  these  primary  organs,  and  make  them  binate 
or  even  temate.  Now  it  is  obvious  that  an  indi- 
vidual, which  begins  with  a  divided  primary 
leaf,  will  have  a  greater  tendency  to  produce  a 
large  number  of  supernumerary  leaflets  than  a 
plant  which  commences  in  the  ordinary  way. 
Or  in  other  words,  the  primary  leaves  afford  a 
sure  criterion  for  the  selection,  and  this  selec- 
tion may  be  made  in  the  seed-pans.  In  conse- 
quence, no  young  individual  with  an  undivided 
primary  leaf  was  planted  out.  Choosing  the 
20  or  30  best  specimens  in  the  seed-pan,  no 
further  selection  was  required,  and  the  whole 
lot  could  be  left  to  cross-fertilization  by  insects. 
The  observation  of  this  distinguishing  mark 
in  the  young  seedlings  has  led  to  the  discover}^ 
of  another  quality  as  a  starting-point  for  fur- 


348  Ever-sporting  Varieties 

tlier  selection.  According  to  the  general  rule 
of  pedigree-culture,  the  seeds  of  each  individual 
plant  are  always  saved  and  sowed  separately. 
This  is  done  even  with  such  species  as  the 
clover,  which  are  infertile  when  self-pollinated, 
and  which  are  incapable  of  artificial  pollina- 
tion on  the  required  scale,  since  each  flower  pro- 
duces only  one  seed.  My  clover  was  always 
left  free  to  be  pollinated  by  insects.  Obviously 
this  must  have  led  to  a  diminution  of  the  differ- 
entiating characters  of  the  individual  plants. 
But  this  does  not  go  far  enough  to  obliterate 
the  differences,  and  the  selection  made  among 
the  seedlings  will  always  throw  out  at  least 
a  large  part  of  those  that  have  suffered  from 
the  cross. 

Leaving  this  discussion,  we  may  inquire 
closer  into  the  nature  of  the  new  criterion  af- 
forded by  the  seedlings.  Two  methods  present 
themselves.  First,  the  choice  of  the  best  seed- 
lings. In  the  second  place  it  becomes  possible 
to  compare  the  parent-plants  by  counting  the 
number  of  deviating  seedlings.  This  leads  to 
the  establishment  of  a  percentage  for  every 
single  parent,  and  gives  data  for  comparisons. 
Two  or  three  hundreds  of  seeds  from  a  parent 
may  easily  be  grown  in  one  pan,  and  in  this 
way  a  sufficiently  high  degTee  of  accuracy 
may  be  reached.     Only  those  parents  that  give 


Five-leaved  Clover  349 

the  highest  percentage  are  chosen,  and  among 
their  progeny  only  the  seedlings  with  trif  oliolate 
primary  leaves  are  planted  out.  The  whole 
procedure  of  the  selection  is  by  this  means  con- 
fined to  the  glasshouse  during  the  spring,  and 
the  beds  need  not  be  large,  nor  do  they  require 
any  special  care  during  the  summer. 

By  this  method  I  brought  my  strain  within 
two  years  up  to  an  average  of  nearly  90  ^  of  the 
seedlings  with  a  divided  primary  leaf.  Around 
this  average  the  real  numbers  fluctuated  be- 
tween the  maximum  of  99;^  and  the  minimum 
of  70^  or  thereabouts.  This  condition  was 
reached  by  the  sixth  generation  in  the  year  189-I-, 
and  has  since  proved  to  be  the  limit,  the  group 
of  figures  remaining  practically  the  same  during 
all  the  succeeding  generations. 

Such  selected  plants  are  very  rich  in  leaves 
with  four,  fi\e  and  six  blades.  Excluding  the 
small  leaves  at  the  tops  of  the  branches,  and 
those  on  the  numerous  weaker  side-branches, 
these  three  groups  include  the  large  majority 
of  all  the  stronger  leaves.  In  summer  the 
range  is  wider,  and  besides  many  trifoliolate 
leaves  the  curiously  shaped  seven-bladed  ones 
are  not  at  all  rare.  In  the  fall  and  in  the  win- 
ter the  range  of  variability  is  narrowed,  and 
at  first  sight  the  plants  often  seem  to  bear  only 
quinquefoliolate  leaves. 


350  Ever-sporting  Varieties 

I  have  cultivated  a  new  generation  of  this 
race  nearly  every  year  since  1894,  using  always 
the  strictest  selection.  This  has  led  to  a  uni- 
form type,  but  has  not  been  adequate  to  produce 
any  further  improvement.  Obviously  the  ex- 
treme limit,  under  the  conditions  of  climate  and 
soil,  has  been  reached.  This  extreme  type  is 
always  dependent  upon  repeated  selection.  No 
constant  variety,  in  the  older  sense,  has  been 
obtained,  nor  was  any  indication  afforded  that 
such  a  type  might  ever  be  produced.  On  the 
contrary,  it  is  manifest  that  the  new  form  be- 
longs to  the  group  of  ever-sporting  varieties. 
It  is  never  quite  free  from  the  old  atavistic 
type  of  the  trifoliolate  leaves,  and  invariably, 
when  external  conditions  become  less  favorable, 
this  atavistic  form  is  apt  to  gain  dominion  over 
the  more  refined  varietal  character.  Rever- 
sions always  occur,  both  partial  and  individual. 

Some  instances  of  these  reversions  may  now 
be  given.  They  are  not  of  such  a  striking  char- 
acter as  tliose  of  the  snapdragon.  Intermediate 
steps  are  always  occurring,  both  in  the  leaves 
themselves,  and  in  the  percentages  of  deviating 
seedlings  of  the  several  parent  plants. 

On  normal  plants  of  my  variety  the  quinque- 
foliolate  leaves  usually  compose  the  majority, 
when  there  are  no  weak  lateral  branches,  or 
when  they  are  left  out  of  consideration.     Next 


Five-leaved  Clover  351 

r 

to  these  come  the  fours  and  the  sixes,  while  the 
trifoliolate  and  seven-bladed  types  are  nearly 
equal  in  number.  But  out  of  a  lot  of  plants, 
grown  from  seed  of  the  same  parent,  it  is  often 
possible  to  choose  some  in  which  one  extreme 
prevails,  and  others  with  a  preponderating 
number  of  leaves  with  the  other  extreme  num- 
ber of  leaflets.  If  seed  from  these  extremes  are 
saved  separately,  one  strain,  that  with  numer- 
ous seven-bladed  leaves  will  remain  true  to  the 
type,  but  the  other  will  diverge  more  or  less, 
producing  leaves  with  a.  varying  number  of  sub- 
divisions. 

Very  few  generations  of  such  opposite  selec- 
tion are  required  to  reduce  the  race  to  an 
utterly  poor  one.  In  three  years  I  was  able  to 
nearly  obliterate  the  type  of  my  variety.  I 
chose  the  seedlings  with  an  undivided  primary 
leaf,  cultivated  them  and  counted  their  off- 
spring separately  after  the  sowing.  I  found 
some  parents  with  only  2  -  3^  of  seedlings  with 
divided  primary  leaves.  And  by  a  repeated 
selection  in  this  retrograde  direction  I  suc- 
ceeded in  getting  a  great  number  of  plants, 
which  during  the  whole  summer  made  only 
very  few  leaves  with  more  than  three  blades. 
But  an  absolute  reversion  could  no  more  be 
reached  in  this  direction  than  in  the  normal 
one.     Any  sowing  without  selection  would  be 


352  Ever-sporting  Varieties 

liable  to  reduce  the  strain  to  an  average  condi- 
tion. 

The  production  of  varietal  and  of  atavistic 
leaves  is  dependent  to  a  high  degree  on 
external  conditions.  It  agrees  with  the  gen- 
eral rule,  that  favorable  circumstances 
strengthen  the  varietal  peculiarities,  while  un- 
favorable conditions  increase  the  number  of  the 
parts  with  the  atavistic  attribute.  These  in- 
fluences may  be  seen  to  have  their  effect  on  the 
single  individuals,  as  well  as  on  the  generations 
growing  from  their  seed.  I  cannot  cite  here  all 
the  experimental  material,  but  a  single  illustra- 
tive example  may  be  given.  I  divided  a  strong 
individual  into  two  parts,  planted  one  in  rich 
soil  and  the  other  in  poor  sand,  and  had  both 
pollinated  by  bees  with  the  pollen  of  some  nor- 
mal individuals  of  my  variety  growing  between 
them.  The  seeds  of  both  were  saved  and  sown 
separately,  and  the  two  lots  of  offspring  culti- 
vated close  to  each  other  under  the  same  ex- 
ternal conditions.  In  the  beginning  no  differ- 
ence was  seen,  but  as  soon  as  the  young  plants 
had  unfolded  three  or  four  leaves,  the  progeny 
of  the  better  nourished  half  of  the  parent-plant 
showed  a  manifest  advance.  This  difference 
increased  rapidly  and  was  easily  seen  in  the 
beds,  even  before  the  flowering  period. 

This  experience  j^robably  gives  an  explana- 


Five-leaved  Clover  35 


o 


tion  why  the  quinquefoliolate  variety  is  so 
seldom  met  with  in  the  wild  state.  For  even  if 
it  did  occur  more  often,  the  plants  would  hardly 
find  circumstances  favorable  enough  for  the 
full  development  of  their  varietal  character. 
They  must  often  be  so  poor  in  anomalous  leaves 
as  to  be  overlooked,  or  to  be  taken  for  instances 
of  the  commonly  occurring  quadrifoliolate 
leaves  and  therefore  as  not  indicating  the  true 
variety. 

In  the  beginning  of  my  discussion  I  have  as- 
serted the  existence  of  two  different  races  of 
**  four-leaved  "  clovers,  a  poor  one  and  a  rich 
one,  and  have  insisted  on  a  sharp  distinction  be- 
tween them.  This  distinction  partly  depends 
on  experiments  with  clover,  but  in  great  part 
on  tests  with  other  plants.  The  previously 
mentioned  circumstance,  that  clover  cannot  be 
pollinated  on  a  sufficiently  large  scale  otherwise 
than  by  insects,  prevents  trials  in  more  than  one 
direction  at  the  same  time  and  in  the  same 
garden.  For  this  reason  I  have  chosen  another 
species  of  clover  to  be  able  to  give  proof  or  dis- 
proof of  the  assertion  quoted. 

This  species  is  the  Italian,  or  crimson  clover, 
which  is  sometimes  also  called  scarlet  clover 
{Trifolium  incarnatum).  It  is  commonly  used 
in  Europe  as  a  crop  on  less  fertile  soils  than 
are  required  by  the  red  clover.     It  is  annual 


354  Ever-sporting  Varieties 

and  erect  and  more  or  less  hairy,  and  has 
stouter  leaves  than  other  kinds  of  clover.  It 
has  oblong  or  cylindrical  heads  with  bright 
crimson  flowers,  and  may  be  considered  as  one 
of  the  most  showy  types.  As  an  annual  it  has 
some  manifest  advantages  over  the  perennial 
species,  especially  in  giving  its  harvest  of  hay 
at  other  seasons  of  the  vear. 

I  found  some  stray  quaternate  leaves  of  this 
plant  some  years  ago,  and  tried  to  win  from 
them,  through  culture  and  selection,  a  race  that 
would  be  as  rich  in  these  anomalies  as  the  red 
clover.  But  the  utmost  care  and  the  most  rigid 
selection,  and  all  the  attention  I  could  afford, 
failed  to  produce  any  result.  It  is  now  ten 
years  since  I  commenced  this  experiment,  and 
more  than  once  I  have  been  willing  to  give  it 
up.  Last  year  (1903)  I  cultivated  some  hun- 
dreds of  selected  plants,  but  though  they  yielded 
a  few  more  instances  of  the  desired  anomaly 
than  in  the  beginning,  no  trace  of  a  truly  rich 
race  could  be  discovered.  The  experimental 
evidence  of  this  failure  shows  at  least  that  strav 
^'  four-leaves  ''  may  occur,  which  do  not  indi- 
cate the  existence  of  a  true  "  four-"  or  ''  five- 
leaved  "  variety. 

This  conception  seems  destined  to  become  of 
great  value  in  the  appreciation  of  anomalies,  as 
they  are  usually  found,  either  in  the  wild  state 


Five-leaved  Clover  355 

or  in  gardens.  And  before  describing  the  de- 
tails of  my  unsuccessful  pedigree-culture,  it  may 
be  as  well  to  give  some  more  instances  of  what 
occurs  in  nature. 

Stray  anomalies  are  of  course  rare,  but  not 
so  rare  that  they  might  not  be  found  in  large 
numbers  when  perseveringly  sought  for. 
Pitcher-like  leaves  may  be  found  on  many  trees 
and  shrubs  and  herbs,  but  ordinarily  one  or 
only  two  of  them  are  seen  in  the  course  of  many 
years  on  the  same  plant,  or  in  the  same  strain. 
In  some  few  instances  they  occur  annually  or 
nearly  so,  as  in  some  individuals  of  the  Euro- 
pean lime-tree  {Tilia  parvifolia)  and  of  the 
common  magnolia  (Magnolia  ohovata).  Many 
of  our  older  cultivated  plants  are  very  rich  in 
anomalies  of  all  kinds,  and  Cyclamen,  Fuchsia, 
Pelargonium  and  some  others  are  notorious 
sources  of  teratologic  phenomena.  Deviations 
in  flowers  may  often  be  seen,  consisting  of 
changes  in  the  normal  number  of  the  several  or- 
gans, or  alterations  in  their  shape  and  color. 
Leaves  may  have  two  tips,  instead  of  one,  the 
mid-vein  being  split  near  the  apex,  and  the  fis- 
sure extending  more  or  less  towards  the  base. 
Rays  of  the  umbels  of  umbelliferous  plants  may 
grow  together  and  become  united  in  groups  of 
two  or  more,  and  in  the  same  way  the  fruits  of 


356  Ever-sporting  Varieties 

the   composites   may   be   united   into    groups. 
Many  other  instances  could  easily  be  given. 

If  we  select  some  of  these  anomalies  for 
breeding-experiments,  our  results  will  not  agree 
throughout,  but  will  tend  to  group  themselves 
under  two  heads.  In  some  cases  the  isolation 
of  the  deviating  individuals  will  at  once  show 
the  existence  of  a  distinct  variety,  which  is 
capable  of  producing  the  anomaly  in  any  de- 
sired number  of  instances,  only  dependent  on 
a  favorable  treatment  and  a  judicious  selection. 
In  other  cases  no  treatment  and  no  selection 
are  adequate  to  give  a  similar  result,  and  the 
anomaly  remains  refractory  despite  all  our  en- 
deavors to  breed  it.  The  cockscomb  and  the 
peloric  fox-glove  are  widely  known  instances  of 
permanent  anomalies,  and  others  will  be  dealt 
with  in  future  lectures.  On  the  other  hand 
I  have  often  tried  in  vain  to  win  an  anomalous 
race  from  an  accidental  deviation,  or  to  isolate 
a  teratologic. variety  out  of  more  common  aber- 
rations. Two  illustrative  examples  may  be 
quoted.  In  our  next  lecture  we  shall  deal  with 
a  curious  phenomenon  in  poppies,  consisting  in 
the  change  of  the  stamens  into  pistils  and  giving 
rise  to  a  bright  crown  of  secondary  capsules 
around  the  central  one.  Similar  anomalies  may 
be  occasionally  met  with  in  other  species  of  the 
same  genus.     But  they  are  rare,  and  may  show 


Five-leaved  Clover  357 

the  conversion  of  only  a  single  stamen  in  the 
described  manner.  I  observed  this  anomaly  in 
a  poppy  called  Papaver  commutatum,  and  sub- 
jected it  during  several  years  to  a  rigid  selec- 
tion of  the  richest  individuals.  No  ameliora- 
tion was  to  be  gained  and  the  culture  had  to  be 
given  up.  In  the  same  way  I  found  on  the  bul- 
bous buttercup  (Ranunculus  hulbosus)  a  strain 
varying  largely  in  the  number  of  the  petals, 
amounting  often  to  Q-S^  and  in  some  flowers 
even  yet  to  higher  figures.  During  five  succeed- 
ing years  I  cultivated  five  generations,  often  in 
large  numbers,  selecting  always  those  which 
had  the  highest  number  of  petals,  throwing  out 
the  remainder  and  saving  the  seed  only  from 
the  very  best  plants.  I  got  a  strain  of  selected 
plants  with  an  average  number  of  nine  petals 
in  every  flower,  and  found  among  4000  flowers 
four  having  20  petals  or  more,  coming  up  even 
to  31  in  one  instance.  But  such  rare  instances 
had  no  influence  whatever  on  the  selection, 
since  thev  were  not  indicative  of  individual 
qualities,  but  occurred  quite  accidentally  on 
flowers  of  plants  having  only  the  average  num- 
ber of  petals.  Now  double  flowers  are  widely 
known  to  occur  in  other  species  of  the  butter- 
cups, both  in  the  cultivated  varieties  and  in 
some  wild  forms.  For  this  reason  it  might  be 
expected  that  through  a  continuous  selection  of 


358  Ever-sporting  Varieties 

the  individuals  with  the  largest  numbers  a 
tendency  to  become  double  would  be  evolved. 
Such,  however,  was  not  the  case.  No  propen- 
sity to  vary  in  any  definite  direction  could  be 
observed.  Quite  on  the  contrary,  an  average 
condition  was  quickly  reached,  and  then  re- 
mained constant,  strongly  counteracting  all 
selection. 

Such  experiences  clearly  show  that  the  same 
anomaly  may  occur  in  different  species,  and  no 
doubt  in  strains  of  the  same  species  from  dif- 
ferent localities,  according  to  at  least  two  dif- 
ferent standards.  The  one  is  to  be  called  the 
poor,  and  the  other  the  rich  variety.  The  first 
always  produces  relatively  few  instances  of  the 
deviation,  the  last  is  apt  to  give  as  many  of  them 
as  desired.  The  first  is  only  half-way  a  variety, 
and  therefore  would  deserve  the  name  of  a  half- 
race  ;  the  second  is  not  yet  a  full  constant  vari- 
ety, but  always  fluctuates  to  and  fro  between  the 
varietal  and  the  specific  mark,  ever-sporting  in 
both  directions.  It  holds  a  middle  position  be- 
tween a  half-race  and  a  variety,  and  there- 
fore might  be  called  a  "  middle-race."  But 
the  term  ever-sporting  variety  seems  more  ade- 
quate to  convey  a  right  idea  of  the  nature  of 
this  curious  type  of  inheritance. 

From  this  discussion  it  will  be  seen  that  the 
behavior  of  the  crimson  clover  is  not  to  be  con- 


Five-leaved  Clover  359 

sidered  as  an  exception,  but  as  a  widely  occur- 
ring type  of  phenomenon,  occurring  perhai)s  in 
all  sorts  of  teratologic  deviations,  and  in  wide 
ranges  of  species  and  genera.  Hence  it  may  be 
considered  worth  while  to  give  some  more  de- 
tails of  this  extended  experiment. 

Ten  years  ago  (1894-5)  I  bought  and  sowed 
about  a  pound  of  seed  of  the  crimson  clover. 
x\mong  many  thousands  of  normal  seedlings  I 
found  two  with  three  and  one  with  four  cotyle- 
dons. Trusting  to  the  empirical  rules  of  corre- 
lation, I  transplanted  these  three  individuals  in 
order  to  isolate  them  in  the  flowering  period. 
One  of  them  produced  during  the  ensuing  sum- 
mer one  four-bladed  and  one  five-bladed  leaf. 
The  seeds  were  saved  separately  and  sown  the 
following  spring  and  the  expected  result  could 
soon  be  seen.  Among  some  250  individual 
plants  I  counted  22  with  one  or  two  deviations, 
and  10  with  from  three  to  nine  four-  or  five- 
bladed  leaves.  Proportions  nearly  similar  have 
been  observed  repeatedly.  Better  nourished  in- 
dividuals have  produced  more  deviating  leaves 
on  one  plant,  partly  owing  to  the  larger  number 
of  stems  and  branches,  and  poor  or  average 
specimens  have  mostly  been  without  any  aber- 
ration or  with  only  one  or  two  abnormal  leaves. 
No  further  improvement  could  be  attained. 
Quadrifoliolate  leaves  were  always  rare,  never 


360  Ever-sporting  Varieties 

attaining  a  number  that  would  put  its  stamp  on 
a  whole  bed.  I  have  endeavored  to  get  some 
six-  and  seven-bladed  crimson  clover  leaves,  but 
in  vain ;  selection,  culture  of  many  hundreds  of 
individuals,  manure,  and  the  best  possible  treat- 
ment has  not  been  adequate  to  produce  them. 
Of  course  I  am  quite  convinced  that  a  repetition 
of  my  experiment  on  a  far  larger  scale  would 
jdeld  the  desired  types,  but  then  only  in  such 
rare  instances  that  they  would  have  no  influence 
whatever  on  the  average,  or  on  the  improve- 
ment of  the  race.  The  eighth  generation  in  the 
year  1903  has  not  been  noticeably  better  than 
the  second  and  third  generations  after  the  first 
selection. 

In  comparing  this  statement  with  the  results 
gained  in  the  experiment  with  the  red  clover, 
the  difference  is  at  once  striking.  In  one  case 
a  rich  variety  was  isolated,  and,  by  better 
treatment  and  sharp  methods  of  selection,  was 
brought  up  in  a  few  years  to  its  highest 
pitch  of  development.  In  the  other  case  a  very 
weak  race  was  shown  to  exist,  and  no  amount 
of  work  and  perseverance  was  adequate  to  im- 
prove it  to  any  noticeable  degree. 

I  wish  to  point  out  that  the  decision  of  what 
is  to  be  expected  from  deviating  specimens  may 
become  manifest  within  one  or  two  generations. 
Even  the  generation  grown  from  the  seeds  of 


Five-leaved  Clover  361 

the  first  observed  aberrant  individuals,  if  gath- 
ered after  sufficient  isolation  during  the  period 
of  blossoming,  may  show  which  type  Oi  in- 
heritance is  present,  whether  it  is  an  unpromis- 
ing half-race,  or  a  richly  endowed  sporting 
variety.  I  have  kept  such  strains  repeatedly 
after  the  first  isolation,  and  a  special  case,  that 
of  cotyledoneous  aberrations,  will  be  dealt  with 
later.  The  first  generation  always  gave  a  final 
decision,  provided  that  a  suitable  method  of 
cultivation  for  the  species  under  observation 
was  found  at  the  beginning.  This  however, 
is  a  condition,  which  it  is  not  at  all  easy  to 
comply  with,  when  new  sorts  are  introduced 
into  a  garden.  Especially  so  when  they  had 
been  collected  in  the  wild  state.  Often  one  or 
two  years,  sometimes  more,  are  necessary  to 
find  the  proper  method  of  sowing,  manuring, 
transplanting  and  other  cultural  methods  satis- 
factory to  the  plants.  Many  wild  species  re- 
quire more  care  and  more  manure  in  gardens 
than  the  finest  garden  flowers.  And  a  large 
number  are  known  to  be  dependent  on  very 
particular  conditions  of  soil. 

One  of  the  most  curious  features  of  anom- 
alies, which  has  been  learned  from  accumulated 
instances,  is  the  fact  that  they  obey  definite 
laws  as  to  their  occurrence  on  the  different 
parts  of  the  plant.     Obviously  such  laws  are 


362  Ever-sporting  Varieties 

not  apparent  as  long  as  each  plant  produces 
only  one  or  two,  or,  at  most,  a  few  instances  of 
the  same  deviation.  On  the  contrary,  any  ex- 
isting regularity  must  betray  itself,  as  soon  as 
a  larger  number  of  instances  is  produced.  A 
rule  of  periodicity  becomes  most  clearly  mani- 
fest in  such  cases. 

This  rule  is  shown  by  no  other  race  in  a  more 
undoubted  and  evident  manner  than  by  the 
*^  five-leaved  "  clover.  Evidently  the  several 
degrees  of  deviation,  going  from  three  to  seven 
leaflets,  may  be  regarded  as  responses  to  differ- 
ent degrees  of  variation,  and  their  distribution 
over  the  stems  and  branches,  or  over  the  whole 
plant,  may  be  considered  as  the  manifestation  of 
the  ever-changing  internal  tendency  to  vary. 

Considered  from  this  point  of  view,  my  plants 
always  showed  a  definite  periodicity  in  this  dis- 
tribution, which  is  the  same  for  the  whole  plant. 
Each  of  them,  and  each  of  the  larger  branches, 
begin  with  atavistic  leaves  or  with  slight  devia- 
tions. These  are  succeeded  by  greater  devia- 
tions, but  only  the  strongest  axes  show  as  many 
as  seven  leaflets  on  a  stalk.  This  ordinarily 
does  not  occur  before  the  height  of  development 
is  reached,  and  often  only  towards  its  close- 
Then  the  deviation  diminishes  rapidly,  return- 
ing often  to  atavistic  leaves  at  the  summit  of  the 
stem  or  branch.     I  give  the  numbers  of  the 


Five-leaved  Clover  363 

leaves  of  a  branch,  in  their  order  from  the  base 
to  the  top.     They  were  as  follows : 

3.    4.    5.    6.     7.    5.    5.    4. 

But  this  is  a  selected  case,  and  such  regular 
examples  of  the  expected  periodicity  are  rarely 
found.  Often  one  or  more  of  the  various  steps 
are  lacking,  or  even  leaves  with  smaller  num- 
bers may  be  interspersed  among  those  with 
larger  numbers  of  leaflets.  But  while  the  regu- 
larity of  the  periodicity  is  in  some  degree 
diminished  by  such  occurrences,  yet  the  rule 
always  holds  good,  when  taken  broadly.  It 
may  be  expressed  by  stating  that  the  bases  and 
apices  have  on  the  average  fewer  leaflets  on  each 
leaf  than  the  middle  parts  of  the  stem  and 
branches,  and  that  the  number  of  leaflets  grad- 
ually^ increases  from  the  base  toward  a  maxi- 
mum, which  is  reached  in  organs  on  the  middle 
or  upper  part  of  the  axis,  and  then  diminishes 
from  this  toward  the  apex. 

This  periodicity  is  not  limited  to  the  stems 
and  branches,  considered  singly,  but  also  holds 
good  in  a  comparison  made  between  the 
branches  of  a  single  stem,  in  regard  to  their  rel- 
ative places  on  that  stem.  So  it  is  also  for  the 
whole  plant.  The  first  stems,  produced  by  the 
subterranean  axis,  ordinarily  show  only  a  low 
maximum  deviation:  the  next  succeeding  being 


364:  Ever-sporting  Varieties 

more  divergent  and  the  last  ones  returning  to 
less  differentiated  forms. 

It  is  evident  that  on  a  given  stem  the  group 
of  deviating  leaves  will  be  extended  upward  and 
downward,  with  the  increase  of  the  number  of 
these  organs.  This  shows  that  a  stem,  or  even 
a  plant,  promises  a  higher  degree  of  differentia- 
tion if  it  commences  with  its  aberration  earlier. 
Hence  it  becomes  possible  to  discern  the  most 
promising  individuals  in  early  youth,  and  this 
conclusion  leads  to  a  very  easy  and  reliable 
method  of  selection,  which  may  be  expressed 
simply  as  follows:  the  seedlings  which  com- 
mence earliest  with  the  production  of  four-  and 
five-foliolate  leaves  are  the  best  and  should  be 
selected  for  the  continuance  of  the  race.  And 
it  is  easily  seen  that  this  rule  agrees  with  that 
given  above,  and  which  was  followed  in  my 
pedigree-culture. 

Furthermore  it  is  seen  that  there  is  a  com- 
plete agreement  between  the  law  of  periodicity 
and  the  responses  of  the  deviations  to  nourish- 
ment and  other  conditions  of  life.  Weak  plants 
only  produce  low  degrees  of  deviation,  the 
stronger  the  individual  becomes,  the  higher  it 
reaches  in  the  scale  of  differentiation,  and  the 
more  often  it  develops  leaves  with  five  or  more 
blades.  Whether  weakness  or  strength  are  de- 
rived from  outer  causes,  or  from  the  internal 


Five-leaved  Clover  365 

succession  of  the  periods  of  life,  is  evidently  of 
no  consequence,  and  in  this  way  the  law  of 
periodicity  may  be  regarded  as  a  special  in- 
stance of  the  more  general  law  of  response  to 
external  conditions. 

The  validity  of  this  law  of  periodicity  is  of 
course  not  limited  to  our  ^^  five-leaved  "  clover. 
Quite  on  the  contrary  it  is  universal  in  ever- 
sporting  varieties.  Moreover  it  may  be  ascer- 
tained and  studied  in  connection  with  the  most 
widely  different  morphologic  abnormalities,  and 
therefore  affords  easily  accessible  material  for 
statistical  inquiry.  I  will  now  give  some  fur- 
ther instances,  but  wish  to  insist  first  upon  the 
necessity  of  an  inquiry  on  a  far  larger  scale, 
as  the  evidence  as  yet  is  very  scanty. 

The  great  celandine  (Chelidonium  ma  jus) 
has  a  very  curious  double  variety.  Its  flowers 
are  simpler  and  much  more  variable  than  in 
ordinary  garden-varieties.  The  process  of 
doubling  consists  mainly  in  a  change  of  stamens 
into  petals.  This  change  is  dependent  on  the 
season.  On  each  stem  the  earliest  flowers  are 
single.  These  are  succeeded  by  blossoms  with 
one  or  two  converted  stamens,  and  towards  the 
summer  this  number  increases  gradually,  attain- 
ing 10  - 11  and  in  some  instances  even  more 
altered  filaments.  Each  vear  the  same  succes- 
sion  may  be  seen  repeating  itself  on  the  stems  of 


366  Ever-sporting  Varieties 

the  old  roots.  Double  tuberous  begonias  are  or- 
dinarily absolutely  sterile  throughout  the  sum- 
mer, but  towards  autumn  the  new  flowers  be- 
come less  and  less  altered,  producing  some  nor- 
mal stamens  and  pistils  among  the  majority  of 
metamorphosed  organs.  From  these  flowers  the 
seeds  are  saved.  Sometimes  similar  flowers 
occur  at  the  beginning  of  the  flowering-period. 
Double  garden-camomiles  (CJirysanthemnm  in- 
odorum  plenissimum)  and  many  other  double 
varieties  of  garden-plants  among  the  great 
family  of  the  composites  are  very  sensitive  to 
external  agencies,  and  their  flower-heads  are 
fuller  the  more  favorable  the  external  condi- 
tions. Towards  the  autumn  many  of  them  pro- 
duce fewer  and  fewer  converted  heads  and  often 
only  these  are  fertile  and  yield  seeds. 

Ascidia  afford  another  instance  of  this 
periodicity,  though  ordinarily  they  are  by  far 
too  rare  to  show  any  regularity  in  their  distri- 
bution. However,  it  is  easy  to  observe  that  on 
lime-trees  they  prefer  the  lower  parts  of  each 
twig,  while  on  magnolias  the  terminal  leaves 
of  the  branches  are  often  pitcher-bearing. 
Ascidia  of  the  white  clover  have  been  found 
in  numbers,  in  my  own  experiment-garden, 
but  always  in  the  springtime.  The  thick- 
leaved  saxifrage  (Saxifraga  crassifolia)  is 
often  very  productive  of  ascidia,  especially  in 


Five-leaved  Clover  367 

the  latter  part  of  the  season,  and  as  these  organs 
may  be  developed  to  very  different  degrees, 
they  afford  fine  material  for  the  study  of  the 
law  of  periodicity.  On  a  garden-cytisus 
(Cytisus  candicans  attleyanus)  I  once  had  the 
good  fortune  to  observe  a  branch  with  ascidia, 
which  ordinarily  are  very  rare  in  this  species. 
It  had  produced  seven  ascidia  in  all,  each 
formed  by  the  conversion  of  one  leaflet  on  the 
trifoliolate  leaves.  The  first  six  leaves  were 
destitute  of  this  malformation  and  were  quite 
normal.  Then  followed  a  group  of  fL\e  leaves, 
constituting  the  maximum  of  the  period.  The 
first  bore  one  small  pitcher-like  blade,  the  sec- 
ond and  third,  each  one  highly  modified  organ, 
the  fourth,  two  ascidia,  and  the  last,  one  leaflet 
with  slightly  connate  margins.  The  whole 
upper  part  of  the  branch  was  normal,  with  the 
exception  of  the  seventeenth  leaf,  which  showed 
a  slight  change  in  the  same  direction.  All  in 
all,  the  tendency  to  produce  ascidia  increased 
from  the  beginning  to  the  tenth  leaf,  and  de- 
creased from  this  upward. 

The  European  Venus'  looking-glass  was  ob- 
served in  my  garden  to  produce  some  quater- 
nate  and  some  quinate  flowers  on  the  same  spec- 
imens. The  quinate  were  placed  at  the  end  of 
the  branches,  those  with  four  petals  and  sepals 
lower  down.     The  peloric  fox-glove  shows  the 


368  Ever-sporting  Varieties 

highest  degree  of  metamorphy  in  the  terminal 
flowers  of  the  stem  itself,  the  weaker  branches 
having  but  little  tendency  towards  the  forma- 
tion of  the  anomaly.  The  European  pine  or 
Pinus  sylvestris  ordinarily  has  two  needles  in 
each  sheath,  but  trifoliolate  sheaths  occur  on  the 
stems  and  stronger  branches,  where  they  prefer, 
as  a  rule,  the  upper  parts  of  the  single  annual 
shoots.  Camellia  japonica  is  often  striped  in 
the  fall  and  during  the  winter,  but  when  flower- 
ing in  the  spring  it  returns  to  the  monochro- 
matic type. 

Peloric  flowers  are  terminal  in  some  cases, 
but  occur  in  the  lower  parts  of  the  flower-spikes 
in  others.  Some  varieties  of  gladiolus  com- 
mence on  each  spike  with  more  or  less  double 
flowers,  which,  higher  up,  are  replaced  by  single 
ones.  A  wide  range  of  bulbs  and  perennial  gar- 
den-plants develop  their  varietal  characters 
only  partly  when  grown  from  seed  and  flower- 
ing for  the  first  time.  The  annual  garden-for- 
get-me-not of  the  Azores  {Myosotis  azorica) 
has  a  variety  with  curiously  enlarged  flowers, 
often  producing  20  or  more  corolla-segments  in 
one  flower.  But  this  number  gradually  dimin- 
ishes as  the  season  advances.  It  would  be  quite 
superfluous  to  give  further  proof  of  the  general 
validity  of  the  law  of  periodicity  in  ever-sport- 
ing varieties. 


Lecture  XIII 


PISTILLODY  IN  POPPIES 


One  of  the  most  curious  anomalies  that  may 
be  met  with  in  ornamental  garden-plants  is  the 
conversion  of  stamens  into  pistils.  It  is  neither 
cormnon  nor  rare,  but  in  most  cases  the  change 
is  so  slight  comparatively  that  it  is  ordinarily 
overlooked.  In  the  opium-poppy,  on  the  con- 
trary, it  is  very  showy,  and  heightens  the  orna- 
mental effect  of  the  young  fruits  after  the  fad- 
ing of  the  flowers.  Here  the  central  capsule  is 
surrounded  by  a  large  crown  of  metamorphosed 
stamens. 

This  peculiarity  has  attracted  the  attention 
both  of  horticulturists  and  of  botanists.  As  a 
rule  not  all  the  stamens  are  changed  in  this  way 
but  only  those  of  the  innermost  rows.  The 
outer  stamens  remain  normal  and  fertile,  and 
the  flowers,  when  pollinated  with  their  own  pol- 
len, bear  as  rich  a  harvest  of  seeds  as  other 
opium-poppies.  The  change  affects  both  the 
filament  and  the  anther,  the  former  of  which  is 
dilated  into  a  sheath.     Within  this  sheath  per- 

369 


370  Ever-sporting  Varieties 

feet  and  more  or  less  numerous  ovules  may  be 
produced.  The  anthers  become  rudhnentary 
and  in  their  place  broad  leafy  flaps  are  de- 
veloped, which  protrude  laterally  from  the  tip 
and  constitute  the  stigmas.  Ordinarily  these 
altered  organs  are  sterile,  but  in  some  instances 
a  very  small  quantity  of  seed  is  produced,  and 
when  testing  their  viability  I  succeeded  in 
raising  a  few  plants  from  them. 

The  same  anomaly  occurs  in  other  plants. 
The  common  wall-flower  (Cheircmthus  Cheiri) 
and  the  houseleek  (Sempervivum  tectorum)  are 
the  best  known  instances.  Both  have  repeated- 
ly been  described  by  various  investigators.  In 
compiling  the  literature  of  this  subject  it  is 
very  interesting  to  observe  the  two  contrasting 
views  respecting  the  nature  of  this  anomaly. 
Some  writers,  and  among  them  Masters  in  his 
^'  Vegetable  Teratology  "  consider  the  devia- 
tions to  be  merely  accidental.  According  to  them 
some  species  are  more  subject  to  this  anomaly 
than  others,  and  the  houseleek  is  said  to  be  very 
prone  to  this  change.  Goeppert,  Hofmeister 
and  others  occasionally  found  the  pistilloid  pop- 
pies in  fields  or  gardens,  and  sowed  their  seeds 
in  order  to  ascertain  whether  the  accidental 
peculiarity  was  inheritable  or  not.  On  the 
other  hand  De  Candolle  in  his  ''  Prodromus  '^ 
mentions  the  pistilloid  wall-flowers  as  a  distinct 


Polycephalic  Poppies  371 

variety,  under  the  name  of  Cheiranthus  Cheiri 
gynantherus,  and  the  analogous  form  of  the 
opium-poppy  is  not  at  all  an  accidental  anomaly, 
but  an  old  true  horticultural  variety,  which 
can  be  bought  everywhere  under  the  names  of 
Papaver  somniferum  monstruosum  or  polyce- 
phalum.  Since  it  is  an  annual  plant,  only  the 
seeds  are  for  sale,  and  this  at  once  gives  a  suffi- 
cient proof  of  its  heredity.  In  all  cases,  where 
it  was  met  with  accidentally  by  botanists,  it  is  to 
be  assumed  that  stray  seeds  had  been  casually 
mixed  with  those  of  other  varieties,  or  that  the 
habit  had  been  transmitted  by  a  spontaneous 
cross. 

Wherever  opportunity  led  to  experiments  on 
heredity,  distinct  races  were  found  to  be  in  pos- 
session of  this  quality,  while  others  were  not. 
It  is  of  no  use  to  cultivate  large  numbers 
of  wall-flowers  in  the  hope  of  one  day  seeing  the 
anomaly  arise ;  the  only  means  is  to  secure  the 
strain  from  those  who  have  got  it.  With  pop- 
pies the  various  varieties  are  so  often  inter- 
crossed by  bees,  that  the  appearance  of  an  acci- 
dental change  may  sometimes  be  produced,  and 
in  the  houseleek  the  pistilloid  variety  seems  to 
be  the  ordinary  one,  the  normal  strain  being 
very  rare  or  perhaps  wholly  wanting. 

Our  three  illustrative  examples  are  good  and 
permanent  races,  producing  their  peculiar  quali- 


372  Ever-sporting  Varieties 

ties  regularly  and  abundantly.  In  this  respect 
they  are  however  very  variable  and  dependent 
on  external  circumstances.  Such  a  regularity 
is  not  met  with  in  other  instances.  Often  pedi- 
gree-experiments lead  to  poor  races,  betraying 
their  tendency  to  deviate  only  from  time  to  time 
and  in  rare  cases.  Such  instances  constitute 
what  we  have  called  in  a  former  lecture,  ^  ^  half- 
races,"  and  their  occurrence  indicates  that  the 
casual  observation  of  an  anomaly  is  not  in  itself 
adequate  to  give  an  opinion  as  to  the  chance  of 
repetition  in  sowing  experiments.  A  large 
number  of  species  seem  to  belong  to  this  case, 
and  their  names  may  be  found  in  the  above 
mentioned  work  by  Masters  and  elsewhere. 
But  no  effort  has  yet  been  made  to  separate 
thoroughly  the  pistilloid  half-races  from  the 
corresponding  ever-sporting  varieties.  Some 
plants  are  recorded  as  being  more  liable  to  this 
peculiarity  than  others. 

Stamens  are  sometimes  replaced  by  open 
carpels  with  naked  ovules  arising  from  their 
edges  and  even  from  their  whole  inner  sur- 
faces. This  may  be  seen  in  distinct  strains  of 
the  cultivated  bulbous  Begonia,  and  more  rarely 
in  primroses.  Here  the  apex  of  the  carpellary 
leaf  is  sometimes  drawn  out  into  a  long  style, 
terminated  by  a  flattened  spatulate  stigma. 

The  pistillody  of  the  stamens  is  frequently 


Polycephalic  Poppies  373 

combined  with  another  deviation  in  the  poppies. 
This  is  the  growing  together  of  some  of  the 
altered  stamens  so  as  to  constitute  smaller  or 
larger  connate  groups.  Often  two  are  united, 
sometimes  three,  four  or  more.  Flowers  with 
numerous  altered  stamens  are  seldom  wholly 
free  from  this  most  undesirable  secondary 
anomaly.  I  call  it  undesirable  with  respect 
to  experiments  on  the  variability  of  the 
character.  For  it  may  easily  be  seen  that 
while  it  is  feasible  to  count  the  stamens 
even  when  converted  into  pistils,  it  is  not 
possible  when  groups  of  them  are  more  or 
less  intimately  united  into  single  bodies.  This 
combination  makes  all  enumeration  difficult  and 
inaccurate  and  often  wholly  unreliable.  In 
such  cases  the  observation  is  limited  to  a  compu- 
tation of  the  degree  of  the  change,  rather  than 
to  a  strict  numerical  inquiry.  Happily  the  re- 
sponses to  the  experimental  influences  are  so 
marked  and  distinct  that  even  this  method  of  de- 
scribing them  has  proved  to  be  wholly  sufficient. 

In  extreme  instances  I  have  seen  all  the 
changed  stamens  of  a  flower  of  the  opium-poppy 
united  into  a  single  body,  so  as  to  form  a  close 
sheath  all  around  the  central  ovary.  Lesser 
sheaths,  surrounding  one-half  or  one-third  of 
the  capsule  are  of  course  less  rarely  met  with. 

Leaving  this  description  of  the  outer  appear- 


374  Ever-sporting  Varieties 

ance  of  our  anomaly,  we  may  now  consider  it 
from  the  double  point  of  view  of  inheritance 
and  variability. 

The  fact  of  inheritance  is  shown  by  the  ex- 
perience of  many  authors,  and  by  the  circum- 
stance already  quoted,  that  the  variety  has  been 
propagated  from  seed  for  more  than  half  a  cen- 
tury, and  may  be  obtained  from  various  seed- 
merchants.  In  respect  to  the  variability,  the 
variety  belongs  to  the  ever-sporting  group,  con- 
stituting a  type  which  is  more  closely  related  to 
the  ''five-leaved  ''  clover  than  to  the  striped 
flowers  or  even  the  double  stocks. 

It  fluctuates  around  an  average  type  with  half 
filled  crowns,  going  as  far  as  possible  in  both 
directions,  but  never  transgressing  either  limit. 
It  is  even  doubtful  whether  the  presumable 
limits  are,  under  ordinary  circumstances,  ever 
reached. ,  Obviously  one  extreme  would  be  the 
conversion  of  all  the  stamens,  and  the  other  the 
absolute  deficiency  of  any  marked  tendency  to 
such  a  change.  Both  may  occur,  and  will  prob- 
ably be  met  with  from  time  to  time.  But  they 
must  be  extremely  rare,  since  in  my  own  exten- 
sive experiments,  which  were  strictly  controlled, 
I  never  was  able  to  find  a  single  instance  of 
either  of  them.  Some  of  the  outer  stamens 
have  always  remained  unchanged,  yielding 
enough  pollen  for  the  artificial  pollination  of 


Polycephalic  Poppies  375 

the  central  ovary,  and  on  the  other  hand  some 
rudmients  of  hardened  filaments  were  always 
left,  even  if  they  were  reduced  to  small  pro- 
tuberances on  the  thalamus  of  the  flower. 

Between  these  extremes  all  grades  occur. 
From  single,  partially  or  wholly  changed 
stamens  upwards  to  150  and  over,  all  steps  may 
be  seen.  It  is  a  true  fluctuating  variability. 
There  is  an  average  of  between  50  and  100,  con- 
stituting a  nearly  filled  crown  around  the  cen- 
tral capsule.  Around  this  average  the  smaller 
deviations  are  most  numerous  and  the  larger 
ones  more  rare.  The  inspection  of  any  bed  of 
the  variety  suffices  to  show  that,  taken  broadly, 
the  ordinary  laws  of  fluctuating  variability  are 
applicable.  No  counting  of  the  single  individ- 
uals is  required  to  dispel  all  doubts  on  this 
point. 

Moreover  all  intermediate  steps  respecting 
the  conversion  of  the  single  stamens  may  nearly 
always  be  seen.  Rarely  all  are  changed  into 
normal  secondary  ovaries  with  a  stigma  and 
with  a  cavity  filled  with  ovules.  Often  the 
stigma  is  incomplete  or  even  almost  wanting,  in 
other  instances  the  ovules  are  lacking  or  the 
cavity  itself  is  only  partially  developed.  Not 
rarely  some  stamens  are  reduced  and  converted 
into  thin  hard  stalks,  without  any  appearance  of 
an  ovary  at  their  tip.    But  then  the  demar- 


376  Ever-sporting  Varieties 

cation  between  them  and  the  thalamus  fails,  so 
that  they  cannot  be  thrown  off  when  the  flower 
fades  away,  but  remain  as  small  stumps  around 
the  base  of  the  more  fully  converted  filaments. 
This  fact  would  frequently  render  the  enumera- 
tion of  the  altered  organs  quite  unreliable. 

For  these  reasons  I  have  chosen  a  group  of 
arbitrary  stages  in  order  to  express  the  degree 
of  deviation  for  a  given  lot  of  plants.  The 
limits  were  chosen  so  as  to  be  sufficiently  trust- 
worthy and  easy  to  ascertain.  In  each  group 
the  members  could  be  counted,  and  a  series  of 
figures  was  reached  by  this  means  which  al- 
lowed of  a  further  comparison  of  the  competing 
sets  of  plants. 

It  should  be  stated  that  in  such  experiments 
and  especially  in  the  case  of  such  a  showy  crite- 
rion as  the  pistilloid  heads  afford  after  the  time 
of  flowering  is  over,  the  inspection  of  the  con- 
trolling beds  at  once  indicates  the  result  of  the 
experiment.  Even  a  hasty  survey  is  in  most 
cases  sufficient  to  get  a  definite  conclusion. 
Where  this  is  not  the  case,  the  counting  of  the 
individuals  of  the  various  groups  often  does  not 
add  to  the  evidence,  and  the  result  remains  un- 
certain. On  the  other  hand,  the  impression 
made  by  the  groups  of  plants  on  the  experi- 
menter and  on  his  casual  visitors,  cannot  well 
be  conveyed  to  the  readers  of  his  account  by 


Poly  cephalic  Poppies  317 

other  means  than  by  figures.  For  this  reason 
the  result  of  the  experhnents  is  expressed  in 
this  way. 

I  made  six  groups.  The  first  includes  tlie 
cases  where  the  whole  circle  is  reduced  to 
small  rudiments.  The  second  shows  1-10  sec- 
ondary capsules.  The  two  following  consti- 
tute half  a  crown  around  the  central  fruit,  the 
third  going  up  to  this  limit,  the  fourth  going 
from  this  limit  to  a  nearly  filled  circle.  Wholly 
filled  circles  of  secondary  capsules  without  gaps 
give  the  two  last  degrees,  the  fifth  requiring 
only  continuity  of  the  circle,  the  sixth  display- 
ing a  large  and  bright  crown  all  around  the 
central  head.  The  fifth  group  ordinarily  in- 
cludes from  90  - 100  altered  stamens,  while  the 
sixth  has  from  100  - 150  of  these  deviating 
parts. 

In  ordinary  cultures  the  third  and  fourth 
group,  with  their  interrupted  crowns,  predomi- 
nate. Large  crowns  are  rare  and  flowers  which 
at  first  sight  seem  to  be  wholly  normal,  occur 
only  under  circumstances  definitely  known  to  be 
unfavorable  to  growth,  and  to  the  development 
of  the  anomalv. 

Having  reached  by  this  means  a  very  simple 
and  easy  method  of  stating  the  facts  shown  by 
equal  lots  under  contrasting  influences,  we  will 
now  make  use  of  it  to  inquire  into  the  relation 


378  Ever-sporting  Varieties 

of  this  exceptionally  high  degree  of  variability 
to  the  inner  and  outer  conditions  of  life. 

As  a  rule,  all  experiments  show  the  existence 
of  such  a  relation.  Unfavorable  conditions  re- 
duce the  numbers  of  altered  stamens,  favorable 
circumstances  raise  it  to  its  highest  point.  This 
holds  true  for  lots  including  hundreds  of  speci- 
mens, but  also  for  the  sundry  heads  of  one  bed, 
and  often  for  one  single  plant. 

We  may  compare  the  terminal  flower  with 
those  of  the  lateral  branches  on  a  plant,  and 
when  no  special  influences  disturb  the  experi- 
ment, the  terminal  head  ordinarily  bears  the 
richest  crown.  If  the  first  has  more  than 
100  metamorphosed  parts,  the  latter  have 
often  less  than  50  on  the  same  plant.  In  poor 
soil,  terminal  heads  are  often  reduced  to  10  -  20 
monstrous  organs,  and  in  such  cases  I  found  the 
lateral  flowers  of  the  same  plants  ordinarily 
with  less  than  10  altered  stamens.  In  some 
cases  I  allowed  the  branches  of  the  third  and 
fourth  degree,  in  other  words,  the  side  twigs  of 
the  first  branches  of  my  selected  plants  to  grow 
out  and  produce  flowers  in  the  fall.  They  were 
ordinarily  weak,  sometimes  very  small,  having 
only  5-9  stigmas  on  their  central  fruit.  Sec- 
ondary capsules  were  not  seen  on  such  flowers, 
even  when  the  experiment  was  repeated  on  a 


Polycephalic  Poppies  379 

somewhat  larger  scale  and  during  a  series  of 
years. 

Among  the  same  lot  of  plants  individual  dif- 
ferences almost  always  occur.  They  are  partly 
due  to  inequalities  already  existing  in  the  seeds, 
and  partly  to  the  diversity  of  the  various  parts 
of  the  same  bed.  Some  of  the  plants  become 
stout  and  have  large  terminal  heads.  Others 
remain  very  weak,  with  a  slender  stem,  small 
leaves  and  undersized  flowers.  The  height  and 
thickness  of  the  stem,  the  growth  of  the  foliage 
and  of  the  axillary  buds  are  the  most  obvious 
measures  of  the  individual  strength  of  the 
plant.  The  development  of  the  terminal  flower 
and  the  size  of  its  ovary  manifestly  depends 
largely  on  this  individual  strength,  as  may  be 
seen  at  once  by  the  inspection  of  any  bed  of 
opium-poppies.  Now  this  size  of  the  head  can 
easily  be  measured,  either  by  its  height  or  cir- 
cumference, or  by  its  weight.  Moreover  we  can 
arrange  them  into  a  series  according  to  their 
size.  If  we  do  this  with  the  polycephalous  vari- 
ety, the  relation  between  individual  strength 
and  degree  of  metamorphosis  at  once  becomes 
manifest.  The  largest  heads  have  the  brightest 
crowns,  and  the  number  of  supernumerary  car- 
pels diminishes  in  nearly  exact  proportion  to  the 
size  of  the  fruits.  Fruits  with  less  than  50  al- 
tered stamens  weighed  on  an  average  5  grams, 


380  Ever-sporting  Varieties 

those  with  50  - 100  such  organs  7  grams  and 
those  with  a  bright  crown  10  grams,  the  appen- 
dices being  removed  before  the  weighing.  Cor- 
responding results  have  been  reached  by  the 
comparison  of  the  height  of  the  capsules  with 
their  abnormal  surroundings.  The  degree  of 
development  of  the  monstrosity  is  shown  by  this 
observation  to  be  directly  dependent  on,  and  in 
a  sense  proportionate  to  the  individual  strength 
of  the  plant. 

The  differences  between  the  specimens  grown 
from  a  single  lot  of  seeds,  for  instance  from 
the  seeds  of  one  self-fertilized  capsule  are,  as  I 
have  said,  partly  due  to  the  divergences  which 
are  always  present  in  a  bed,  even  if  the  utmost 
care  has  been  taken  to  make  it  as  uniform  as 
possible.  These  local  differences  are  ordinarily 
underrated  and  overlooked,  and  it  is  often  con- 
sidered to  be  sufficient  to  cultivate  small  lots  of 
plants  under  apparently  similar  conditions  on 
neighboring  beds,  to  be  justified  in  imputing  all 
the  observed  deviations  of  the  plants  to  heredi- 
tary inequalities.  This  of  course  is  true  for 
large  lots,  whenever  the  averages  only  are  com- 
pared. In  smaller  experiments  the  external  con- 
ditions of  the  single  individuals  should  always 
be  considered  carefully.  Lots  of  one  or  two 
square  meters  suffice  for  such  comparisons,  but 
smaller  lots  are  always  subject  to  chances  and 


PolycephaUc  Poppies  381 

possibilities,  which  should  never  be  left  out  of 
consideration. 

Therefore  I  will  now  point  out  some  circum- 
stances, which  are  ordinarily  different  on  va- 
rious parts  of  one  and  the  same  bed. 

In  the  first  place  comes  the  inequality  of  the 
seeds  themselves.  Some  of  them  will  germi- 
nate earlier  and  others  later.  Those  that  dis- 
play their  cotyledons  on  a  sunny  day  will  be 
able  to  begin  at  once  with  the  production  of 
organic  food.  Others  appear  in  bad  weather, 
and  will  thus  be  retarded  in  their  development. 
These  effects  are  of  a  cumulative  nature  as 
the  young  plants  must  profit  by  every  hour  of 
sunshine,  according  to  the  size  of  the  cotyledons. 
Any  inequality  between  two  young  seedlings  is 
apt  to  be  increased  by  this  cumulative  effect. 

The  same  holds  good  for  the  soil  of  the  bed. 
It  is  simply  impossible  to  mix  the  manure  so 
equally  that  all  individuals  receive  the  same 
amount  of  it  from  the  very  beginning.  I  am  in 
the  habit  of  using  manures  in  a  dry  and  pulver- 
ized condition,  of  giving  definite  quantities  to 
each  square  meter,  and  of  taking  the  utmost 
care  to  get  equal  distribution  and  mixture  with 
the  soil,  always  being  present  myself  during  this 
most  important  operation.  Nevertheless  it  is 
impossible  to  make  the  nourishment  exactly 
equal  for  all  the  plants  of  even  a  small  bed. 


382  Ever-sporting  Varieties 

Any  inequality  from  this  cause  will  increase 
the  difference  in  the  size  of  the  young  leaves, 
augment  the  inequality  of  their  production  of 
organic  matter  and  for  this  reason  go  on  in  an 
ever  increasing  rate. 

Rain  and  spraying,  or  on  the  other  hand  dry- 
ness of  the  soil,  have  still  greater  consequences. 
The  slightest  unevenness  of  the  surface  will 
cause  some  spots  to  dry  rapidly  and  others  to 
retain  moisture  during  hours  and  even  some- 
times during  days. 

Seeds,  germinating  in  such  little  moist  de- 
pressions grow  regularly  and  rapidly,  while 
those  on  the  dryer  elevations  may  be  retarded 
for  hours  and  days,  before  fully  unfurling  their 
seed-leaves.  After  heavy  rains  these  differ- 
ences may  be  observed  to  increase  continu- 
ally, and  in  some  instances  I  found  that  plants 
were  produced  only  on  the  wet  spots,  while  the 
dry  places  remained  perfectly  bare.  From  this 
the  wet  spots  seem  to  be  the  most  favorable,  but 
on  the  other  hand,  seeds  may  come  to  germinate 
there  too  numerously  and  so  closely  that  the 
young  plants  will  be  crowded  together  and  find 
neither  space  nor  light  enough,  for  a  free  and 
perfect  development.  The  advantage  may 
change  to  disadvantage  in  this  way  unless  the 
superfluous  individuals  are  weeded  out  in  due 
time. 


Polycephalic  Poppies  383 

From  all  these  and  other  reasons  some  plants 
will  be  favored  by  the  external  conditions  from 
the  beginning,  while  others  will  be  retarded,  and 
the  effects  will  gradually  increase  until  at  last 
they  become  sufficient  to  account  for  a  consider- 
able amount  of  individual  variability.  There 
is  no  doubt  that  the  difference  in  the  strength  of 
the  plant  and  in  the  size  of  the  capsules,  going 
from  5-10  grams  for  a  single  fruit,  are  for  the 
most  part  due  to  these  unavoidable  circum- 
stances. I  have  tried  all  conceivable  means  to 
find  remedies  for  these  difficulties,  but  only  by 
sowing  my  seeds  in  pans  in  a  glass-house  have 
I  been  able  to  reach  more  constant  and  equal 
conditions.  But  unfortunately  such  a  method 
requires  the  planting  out  of  the  young  seed- 
lings in  the  beginning  of  the  summer,  and  this 
operation  is  not  without  danger  for  opium-pop- 
pies, and  especially  not  without  important  influ- 
ence on  the  monstrosity  of  the  pisiilloid  variety. 
Consequently  my  sowings  of  this  plant  have 
nearly  always  been  made  in  the  beds. 

In  order  to  show  how  great  the  influence  of  all 
these  little  things  may  become,  we  only  have  to 
make  two  sowings  on  neighboring  beds  and  un- 
der conditions  which  have  carefully  been  made 
as  equal  as  possible.  If  we  use  for  these  con- 
trolling experiments  seeds  from  one  and  the 
same  capsule,  it  will  soon  become  evident  that 


384  Ever-sporting  Varieties 

no  exact  similarity  between  the  two  lots  may  be 
expected.  Such  differences  as  may  be  seen  in 
these  cases  are  therefore  never  to  be  considered 
of  value  when  comparing  two  lots  of  seeds  of 
different  origin,  or  under  varying  conditions. 
No  amount  of  accuracy  in  the  estimation  of  the 
results  of  a  trial,  or  in  the  counting  out  of  the 
several  degrees  of  the  anomaly,  is  adequate  to 
overcome  the  inaccuracy  resulting  from  these 
differences. 

It  is  certainly  of  great  importance  to  have  a 
correct  conception  in  regard  to  the  influence  of 
the  surrounding  conditions  on  the  growth  of  a 
plant  and  on  the  development  of  the  attribute  we 
are  to  deal  with.  No  less  important  is  the  ques- 
tion of  the  sensibility  of  the  plants  to  these  fac- 
tors. Obviously  this  sensibility  must  not  be 
expected  to  remain  the  same  during  the  entire 
life-period,  and  periods  of  stronger  and  of 
weaker  responses  may  be  discerned. 

In  the  first  place  it  is  evident  that  external  or 
inner  influences  are  able  to  change  the  direction 
of  the  development  of  an  organ  only  so  long  as 
this  development  is  not  yet  hiMj  finished.  In 
the  young  flower-bud  of  the  pistilloid  poppy 
there  must  evidently  be  some  moment  in  which 
it  is  definitely  decided  whether  the  young 
stamens  will  grow  out  normally  or  become  meta- 
morphosed into  secondary  pistils.     From  this 


Polycephalic  Poppies  385 

moment  no  further  change  of  external  condi- 
tions is  able  to  produce  a  corresponding  change 
in  the  degree  of  the  anomaly.  The  indi- 
vidual strength  of  the  whole  plant  may  still  be 
affected  in  a  more  or  less  manifest  degree,  but 
the  number  of  converted  stamens  of  the  flower 
has  been  definitely  fixed.  The  sensitive  period 
has  terminated. 

In  order  to  determine  the  exact  moment  of 
this  termination  of  the  period  of  sensibility,  I 
have  followed  the  development  of  the  flower- 
buds  during  the  first  weeks  of  the  life  of  the 
young  plants.  The  terminal  flower  may  al- 
ready be  seen  in  young  plants  only  seven  weeks 
old,  with  a  stem  not  exceeding  5-6  cm.  in 
height  and  a  flower-bud  with  a  diameter  of 
nearly  1mm.,  in  which  the  stamens  and  sec- 
ondary pistils  are  already  discernible,  but  still 
in  the  condition  of  small  rounded  protuberances 
on  the  thalamus.  Though  it  is  not  possible  at 
that  time  to  observe  any  difference  between  the 
future  normal  and  converted  stamens,  it  does 
not  seem  doubtful  that  the  development  is  so  far 
advanced,  that  in  the  inner  tissues  the  decision 
has  already  definitely  been  taken.  In  the  next 
few  days  this  decision  rapidly  becomes  vis- 
ible, and  the  different  parts  of  the  normal 
stamens  and  the  metamorphosed  carpels  soon 
become   apparent.     From  this   observation  it 


386  Ever-sporting  Varieties 

can  be  inferred  that  the  sensitive  period  of  the 
anomaly  is  limited  for  the  terminal  flower-head, 
to  the  first  few  weeks  of  the  life  of  the  young 
plants.  The  secondary  heads  manifestly  leave 
this  period  at  a  somewhat  later  stage. 

In  order  to  prove  the  accuracy  of  this  con- 
clusion I  have  tried  to  injure  the  anomalies 
after  the  expiration  of  the  first  six  or  seven 
weeks.  I  deprived  them  of  their  leaves,  and 
damaged  them  in  different  ways.  I  succeeded 
in  making  them  very  weak  and  slender,  without 
being  able  to  diminish  the  number  of  the  super- 
numerary carpels.  The  proportionality  of  the 
size  of  the  central  fruit  and  the  development  of 
the  surrounding  crown  can  often  be  modified  or 
even  destroj^ed  by  this  means,  and  the  apparent 
exceptions  from  this  rule,  which  are  often  ob- 
served, may  find  their  explanation  in  this  way. 

In  the  second  place  I  have  tried  to  change  the 
development  of  the  anomaly  during  the  period 
of  sensibility,  and  even  in  the  last  part  of  it. 
This  experiment  succeeded  fully  when  carried 
out  within  the  fifth  or  sixth  week  after  the  be- 
ginning of  the  germination.  As  means  of  in- 
jury I  transplanted  the  young  plants.  To  this 
end  I  sowed  my  seeds  in  pans  in  unmanured  soil, 
planted  them  out  in  little  pots  with  richly  pre- 
pared earth,  grew  them  in  these  during  a  few 
weeks  and  afterwards  transferred  them  to  the 


Polycephalic  Poppies  387 

beds,  taking  care  that  the  pots  were  removed, 
but  the  balls  of  earth  not  broken. 

In  consequence  of  this  treatment  the  plants 
became  very  large  and  strong,  with  luxuriant 
foliage  and  relatively  numerous  large  flowers 
and  fruits.  But  almost  without  exception  they 
were  poor  in  anomalous  stamens,  at  least  so  on 
the  terminal  heads.  On  a  lot  of  some  70  plants 
more  than  50  had  less  than  half  a  crown  of  sec- 
ondary capsules,  while  from  the  same  packet  of 
seed  the  control-plants  gave  in  an  equal  number 
more  than  half  of  filled  crowns  on  all  plants  with 
the  exception  of  ^we  weak  specimens. 

It  is  curious  to  compare  such  artificially  in- 
jured plants  with  the  ordinary  cultures. 
Strong  stems  and  heavy  fruits,  which  otherwise 
are  always  indicative  of  showy  crowns,  now 
bear  fruits  wholly  or  nearly  destitute  of  any 
anomalous  change.  The  commonly  prevailing 
rule  seems  to  be  reversed,  showing  thereby  the 
possibility  of  abolishing  the  correlation  between 
individual  strength  and  anomaly  by  an  artificial 
encroachment  upon  the  normal  conditions. 

Aside  from  these  considerations  the  experi- 
ments clearly  give  proof  of  the  existence  of  a 
period  of  sensibility  limited  to  the  first  weeks  of 
the  life  of  the  plant  for  the  terminal  flower. 
This  knowledge  enables  us  to  explain  many  ap- 


388  Ever-sporting  Varieties 

parent  abnormalities,  which  may  occur  in  the 
experiments. 

We  now  may  take  a  broader  view  of  the  pe- 
riod of  sensibility.  Evidently  the  response  to 
external  influences  will  be  greater  the  younger 
the  organ.  Sensibility  will  gradually  diminish, 
and  the  phenomena  observed  in  the  last  part 
of  this  period  may  be  considered  as  the  last  re- 
mainder of  a  reaction  which  previously  must 
have  been  much  stronger  and  much  readier,  pro- 
viding that  it  would  be  possible  to  isolate  them 
from,  and  contrast  them  with,  the  other  re- 
sponses of  the  same  plant. 

With  the  light  thus  cast  upon  the  question, 
we  may  conclude  that  the  sensitive  period  com- 
mences not  only  at  the  beginning  of  the  germi- 
nation, but  must  also  be  considered  to  include 
the  life  of  the  seed  itself.  From  the  moment 
of  fertilization  and  the  formation  of  the 
young  embryo  the  development  must  be  sub- 
jected to  the  influence  of  external  agencies 
which  determine  the  direction  it  will  take  and 
the  degree  of  development  it  will  finally  be  able 
to  acquire.  Probably  the  time  of  growth  of 
the  embryo  and  of  the  ripening  of  the  seed 
correspond  exactly  to  the  period  of  highest 
sensibility.  This  period  is  only  interrupted 
during  the  resting  stage  of  the  seed,  to  be  re- 
peated in  germination.     Afterwards  the  sensi- 


Poly  cephalic  Poppies  389 

bility  slowly  and  gradually  decreases,  to  end 
with  the  definite  decision  of  all  further  growth 
sometime  before  the  outer  form  of  the  organ  be- 
comes visible  under  the  microscope.  The  last 
period  of  life  includes  only  an  expansion  of  the 
tissues,  which  may  still  have  some  influence  on 
their  final  size,  but  not  on  their  form.  This 
has  been  definitely  arrested  before  the  end  of 
the  sensitive  period,  and  ordinarily  before  the 
com,mencement  of  that  rapid  development, 
which  is  usually  designated  by  the  name  of 
growth,  as  contrasted  with  evolution. 

Within  the  seed  the  evolution  of  the  young 
plant  manifestly  depends  upon  the  qualities 
and  life-conditions  of  the  parent-plant.  The 
stronger  this  is,  and  the  more  favorable  circum- 
stances it  is  placed  under,  the  more  food  will  be 
available  for  the  seed,  and  the  healthier  will  be 
the  development  of  the  embryo.  Only  well- 
nourished  plants  give  well-nourished  seeds,  and 
the  qualities  of  each  plant  are  for  this  reason 
at  least,  partly  dependent  on  the  properties  of 
its  parents  and  even  of  its  grandparents. 

From  these  considerations  the  inference  is 
forced  upon  us  that  the  apparently  hereditary 
differences,  which  are  observed  to  exist  among 
the  seeds  of  a  species  or  a  variety  and  even  of  a 
single  strain  or  a  single  parent-plant,  may  for 
a  large  part,  and  perhaps  wholly,  be  the  result 


odiJ  Ever-sporting  Varieties 

of  the  life-conditions  of  their  parents  and 
grandparents.  Within  the  race  all  variability 
would  in  this  way  be  reduced  to  the  effects 
of  external  circumstances.  Among  these  nour- 
ishment is  no  doubt  the  most  momentous, 
and  this  to  such  a  degree  that  older  writers 
designated  the  external  conditions  by  the  term 
nourishment.  According  to  Knight  nutrition 
reigns  supreme  in  the  whole  realm  of  vari- 
ability, the  kind  of  food  and  the  method  of  nour- 
ishment coming  into  consideration  only  in  a  sec- 
ondary way.  The  amount  of  useful  nutrition 
is  the  all-important  factor. 

If  this  is  so,  and  if  nutrition  decides  the  de- 
gree of  deviation  of  any  given  character,  the 
widest  deviating  individuals  are  the  best  nour- 
ished ones.  The  best  nourished  not  only  dur- 
ing the  period  of  sensibility  of  the  attribute  un- 
der consideration,  but  also  in  the  broadest  sense 
of  the  word. 

This  discussion  casts  a  curious  light  upon  the 
whole  question  of  selection.  Not  of  course 
upon  the  choice  of  elementary  species  or  varie- 
ties out  of  the  original  motley  assembly  which 
nature  and  old  cultures  offer  us,  but  upon  the 
selection  of  the  best  individuals  for  isolation  and 
for  the  improvement  of  the  race.  These  are, 
according  to  my  views,  only  the  best  nourished 
ones.     Their  external  conditions  have  been  the 


Poly  cephalic  Poppies  391 

most  favorable,  not  only  from  the  beginning  of 
their  own  life  in  the  field,  but  also  during  their 
embryonic  stages,  and  even  during  the  prepara- 
tion of  these  latter  in  the  life  of  their  parents 
and  perhaps  even  their  grandparents.  Selec- 
tion then,  would  only  be  the  choice  of  the  best 
nourished  individuals. 

In  connection  with  the  foregoing  arguments 
I  have  tried  to  separate  the  choicest  of  the  pop- 
pies with  the  largest  crown  of  pistilloid  stamens, 
from  the  most  vigorous  individuals.  As  we 
have  already  seen,  these  two  attributes  are 
as  a  rule  proportional  to  one  another.  Excep- 
tions occur,  but  they  may  be  explained  by  some 
later  changes  in  the  external  circumstances,  as 
I  have  also  pointed  out.  As  a  rule,  these  ex- 
ceptions are  large  fruits  with  comparatively  too 
few  converted  stamens;  they  are  exactly  the 
contrary  from  what  is  required  for  a  selection. 
Or  plants,  which  from  the  beginning  were 
robust,  may  have  become  crowded  together  by 
further  growth,  and  for  these  reasons  become 
weaker  than  their  congeners,  though  retaining 
the  full  development  of  the  staminodal  crown, 
which  was  fixed  during  the  sensitive  period  and 
before  the  crowding.  I  have  searched  my  beds 
yearly  for  several  years  in  vain  to  find  individ- 
uals which  might  recommend  themselves  for  se- 
lection without  having  the  stamp  of  permanent. 


392  Ever-sporting  Varieties 

or  at  least  temporarily  better,  nourishment.  No 
starting-point  for  such  an  independent  selection 
has  ever  been  met  with. 

Summing  up  the  consequences  of  this  some- 
what extended  discussion,  we  may  state  it  as  a 
rule  that  a  general  proportion  between  the  in- 
dividual strength  and  the  degree  of  develop- 
ment of  the  anomaly  exists.  And  from  this 
point  of  view  it  is  easy  to  see  that  all  external 
causes  which  are  known  to  affect  the  one,  must 
be  expected  to  influence  the  other  also. 

It  will  therefore  hardly  be  necessary  to  give 
a  full  description  of  all  my  experiments  on  the 
relations  of  the  monstrosity  to  external  condi- 
tions.   A  hasty  survey  will  suffice. 

This  survey  is  not  only  intended  to  convey  an 
idea  of  the  relations  of  pistilloid  poppies  to 
their  environment,  but  may  serve  as  an  ex- 
ample of  the  principle  involved.  According 
to  my  experience  with  a  large  range  of  other 
anomalies,  the  same  rule  prevails  everywhere. 
And  this  rule  is  so  simple  that  exact  knowledge 
of  one  instance  may  be  considered  as  sufficient 
to  enable  us  to  calculate  from  analogy  what  is 
to  be  expected  from  a  given  treatment  of  any 
other  anomaly.  Our  appreciation  of  observed 
facts  and  the  conditions  to  be  chosen  for 
intended  cultures  are  largely  dependent  on  such 
calculations.    What  I  am  now  going  to  describe 


Polycephalic  Poppies  393 

is  to  be  considered  therefore  as  an  experimental 
basis  for  such  expectations. 

First  of  all  comes  the  question  how  many  in- 
dividuals are  to  be  grown  in  a  given  place. 
When  sowing  plants  for  experimental  purposes 
it  is  always  best  to  sow  in  rows,  and  to  give  as 
few  seeds  to  each  row  as  possible,  so  as  to  in- 
sure all  necessary  space  to  the  young  plants. 
On  the  other  hand  the  seeds  do  not  all  germi- 
nate, and  after  sowing  too  thinly,  gaps  may  ap- 
pear in  the  rows.  This  would  cause  not  only  a 
loss  of  space,  but  an  inequality  between  the 
plants  in  later  life,  as  those  nearest  the  gaps 
would  have  more  space  and  more  light,  and  a 
larger  area  for  their  roots  than  those  growing 
in  the  unbroken  rows.  Hence  the  necessity  of 
using  large  quantities  of  seed  and  of  weeding 
out  a  majority  of  young  plants  on  the  spots 
where  the  greatest  numbers  germinate. 

Crowded  cultures  as  a  rule,  will  give  weak 
plants  with  thin  stems,  mostly  unbranched  and 
bearing  only  small  capsules.  According  to  the 
rule,  these  will  produce  imperfect  crowns  of  sec- 
ondary pistils.  The  result  of  any  culture  will 
thus  be  dependent  to  a  high  degree  on  the  num- 
ber of  individuals  per  square  meter.  I  have 
sown  two  similar  and  neighboring  beds  with 
the  thoroughly  mixed  seeds  of  parent-plants  of 
the   same  strain  and  culture,  using  as  much 


o94  Ever-sporting  Varieties 

as  2.5  cub.  cm.  per  square  meter.  On  one  of  the 
beds  I  left  all  the  germinating  plants  untouched 
and  nearly  500  of  them  flowered,  but  among 
them  360  were  almost  without  pistillody,  and 
only  10  had  full  crowns.  In  the  other  bed  1 
weeded  away  more  than  half  of  the  young 
plants,  leaving  only  some  150  individuals  and  got 
32  with  a  full  crown,  nearly  100  with  half  crowns 
and  only  25  apparently  without  monstrosity. 

These  figures  are  very  striking.  From  the 
same  quantity  of  seed,  in  equal  spaces,  by  sim- 
ilar exposure  and  treatment  I  got  10  fully  de- 
veloped instances  in  one  and  32  in  the  other 
case.  The  weeding  out  of  supernumerary  indi- 
viduals had  not  only  increased  the  percentage 
of  bright  crowns,  but  also  their  absolute  num- 
ber per  square  meter.  So  the  greatest  number 
of  anomalies  upon  a  given  space  may  be  ob- 
tained by  taking  care  that  not  too  many  plants 
are  grown  upon  it :  any  increase  of  the  number 
beyond  a  certain  limit  will  diminish  the  prob- 
ability of  obtaining  these  structures.  The  most 
successful  cultures  may  be  made  after  the  max- 
imum number  of  individuals  per  unit  of  area 
has  been  determined.  A  control-experiment 
was  made  under  the  same  conditions  and  with 
the  same  seed,  but  allowing  much  less  for 
the  same  space.  I  sowed  only  1  cu.  cm.  on  my 
bed  of  2  square  meters,  and  thereby  avoided 


Poli/cephalic  Popples  395 

nearly  all  weeding  out.  I  got  120  plants,  and 
among  them  30  with  full  crowns  of  converted 
stamens,  practically  the  same  number  as  after 
the  weeding  out  in  the  first  experiment.  This 
shows  that  smaller  quantities  of  seed  give  an 
equal  chance  for  a  greater  number  of  large 
crowns,  and  should  therefore  always  be  pre- 
ferred, as  it  saves  both  seed  and  labor. 

Weeding  out  is  a  somewhat  dangerous  oper- 
ation in  a  comparative  trial.  Any  one  who  has 
done  it  often,  knows  that  there  is  a  strong 
propensity  to  root  out  the  weaker  plants  and  to 
spare  the  stronger  ones.  Obviously  this  is  the 
best  way  for  ordinary  purposes,  but  for  com- 
parisons evidently  one  should  not  discriminate. 
This  rule  is  very  difficult  in  practice,  and  for 
this  reason  one  should  never  sow  more  than  is 
absolutely  required  to  meet  all  requirements. 

Our  second  point  is  the  manuring  of  the  soil. 
This  is  always  of  the  highest  importance,  both 
for  normal  and  for  anomalous  attributes.  The 
conversion  of  the  stamens  into  pistils  is  in  a 
large  measure  dependent  upon  the  conditions  of 
the  soil.  I  made  a  trial  with  some  800  flowering 
plants,  using  one  sample  of  seed,  but  sowing 
one-third  on  richly  manured  soil,  one-third  on 
an  unprepared  bed  of  my  garden,  and  one-third 
on  nearly  pure  sand.  In  all  other  respects  the 
three  groups  were  treated  in  the  same  way.     Of 


396  Ever-sporting  Varieties 

the  manured  plants  one-half  gave  full  crowns, 
of  the  non-manured  only  one-fifth,  and  on  the 
sandy  soil  a  still  smaller  proportion.  Other 
trials  led  to  the  same  results.  I  have  often  made 
use  of  steamed  and  ground  horn,  which  is  a  ma- 
nure very  rich  in  nitrogenous  substances.  One- 
eighth  of  a  kilo  per  square  meter  is  an  ample 
amount.  And  its  effect  was  to  increase  the 
nmnber  of  full  crowns  to  an  exceptional  degree. 

In  the  controlling  trial  and  under  ordinary 
circumstances  this  figure  reached  some  50^, 
but  with  ground  horn  it  came  up  as  high 
as  90^.  We  may  state  this  result  by  the 
very  striking  assertion  that  the  number  of  large 
crowns  in  a  given  culture  may  be  nearly  doubled 
by  rich  manure. 

All  other  external  conditions  act  in  a  similar 
manner.  The  best  treatment  is  required  to  at- 
tain the  best  result.  A  sunny  exposure  is  one 
of  the  most  essential  requisites,  and  in  some  at- 
tempts to  cultivate  my  poppies  in  the  shade,  I 
found  the  pistillody  strongly  reduced,  not  a 
single  full  crown  being  found  in  the  whole  lot. 
Often  the  weather  may  be  hurtful,  especially 
during  the  earlier  stages  of  the  plants.  I  pro- 
tected my  beds  during  several  trials  by  covering 
them  with  glass  for  a  few  weeks,  until  the  young 
plants  reached  the  glass  covering.  I  got  a  nor- 
mal number  of  full  crowns,  some  55%,  at  a  time 


Polycephalic  Poppies  397 

when  the  weather  was  so  bad  as  to  reduce  the 
number  in  the  control  experiments  to  10%. 

It  would  be  quite  superfluous  to  give  more  de- 
tails or  to  describe  additional  experiments. 
Suffice  to  say,  that  the  results  all  point  in  the 
same  direction,  and  that  pistillody  of  the  pop- 
pies always  clearly  responds  to  the  treatment, 
especially  to  external  conditions  during  the  first 
few  weeks,  that  is,  during  the  period  of  sensi- 
tiveness. The  healthier  and  the  stronger  the 
plants  the  more  fully  they  will  develop  their 
anomaly. 

In  conclusion  something  is  to  be  said  about 
the  choice  of  the  seed.  Obviously  it  is  possible 
to  compare  seeds  of  different  origin  by  sowing 
and  treating  them  in  the  same  way,  giving  at- 
tention to  all  the  points  above  mentioned.  In 
doing  so  the  first  question  will  be,  whether  there 
is  a  difference  between  the  seeds  of  strong 
plants  with  a  bright  crown  around  the  head  and 
those  of  weaker  individuals  with  lesser  develop- 
ment of  the  anomaly.  It  is  evident  that  such  a 
difference  must  be  expected,  since  the  nutrition 
of  the  seed  takes  place  during  the  period  of  the 
greatest  sensitiveness. 

But  the  experiments  will  show  whether  this 
effect  holds  good  against  the  influences  which 
tend  to  change  the  direction  of  the  development 
of  the  anomaly  during  the  time  of  germination. 


398  Ever-sporting  Varieties 

The  result  of  my  attempt  has  shown  that  the 
choice  of  the  seeds  has  a  manifest  influence  upon 
the  ultimate  development  of  the  monstrosity,  but 
that  this  influence  is  not  strong  enough  to  over- 
whelm all  other  factors. 

The  choice  of  the  fullest  or  smallest  crowns 
may  be  repeated  during  succeeding  generations, 
and  each  time  compared  with  a  culture  under 
average  conditions.  By  this  means  we  come  to 
true  selection-experiments,  and  these  result  in 
a  notable  and  rapid  change  of  the  whole  strain. 
By  selecting  the  brightest  crowns  I  have  come 
up  in  three  years  from  40  to  90  and  ultimately 
to  120  converted  stamens  in  the  best  flower  of 
my  culture,  and  in  selecting  the  smallest  crowns 
I  was  able  in  three  j'ears  to  exclude  nearly  all 
good  crowns,  and  to  make  cultures  in  which 
heads  with  less  than  half-filled  crowns  consti- 
tuted the  majority.  But  such  selected  strains 
always  remain  very  sensitive  to  treatment,  and 
by  changing  the  conditions  the  effect  may  be 
wholly  lost  in  a  single  year,  or  even  turned 
in  the  contrary  direction.  In  other  words,  the 
anomaly  is  more  dependent  on  external  condi- 
tions during  the  germinating  period  than  on  the 
choice  of  the  seeds,  providing  these  belong  to 
the  pistilloid  variety  and  have  not  deteriorated 
by  some  crossing  with  other  sorts. 

At  the  beginning  of  this  lecture  I  stated  that 


Polycephalic  Poppies  399 

no  selection  is  adequate  to  produce  either  a  pure 
strain  of  brightly  crowned  flower-heads  without 
atavism,  or  to  conduce  to  an  absolute  and  per- 
manent loss  of  the  anomaly.  During  a  series  of 
years  I  have  tested  my  plants  in  both  directions, 
but  without  the  least  effect.  Limits  are  soon 
reached  on  both  sides,  and  to  transgress  these 
seems  quite  impossible. 

Taking  these  limits  as  the  marks  of  the 
variety,  and  considering  all  fluctuations  between 
them  as  responses  to  external  influences  work- 
ing during  the  life  of  the  individual  or  govern- 
ing the  ripening  of  the  seeds,  we  get  a  clear  pic- 
ture of  a  permanent  ever-sporting  type.  The 
limits  are  absolutely  permanent  during  the 
whole  existence  of  this  already  old  variety. 
They  never  change.  But  they  include  so  wide  a 
range  of  variability  that  the  extremes  may  be 
said  to  sport  into  one  another,  so  much  the  more 
so  as  one  of  the  extremes  is  to  be  considered 
morphologically  as  the  type  of  the  variation, 
while  the  other  extreme  can  hardly  be  distin- 
guished from  the  normal  form  of  the  species. 


Lecture  XIV 

MONSTROSITIES 

I  have  previously  dealt  with  the  question  of 
the  hereditary  tendencies  that  cause  monstros- 
ities. These  tendencies  are  not  always  ident- 
ical for  the  same  anomaly.  Two  different 
types  may,  generally,  be  distinguished.  One  of 
them  constitutes  a  poor  variety,  the  other  a  rich 
one.  But  this  latter  is  abundant  and  the  first 
one  is  poor  in  instances  of  exactly  the  same  con- 
formation. Therefore  the  difference  only  lies 
in  the  frequency  of  the  anomaly,  and  not  in  its 
visible  features.  In  discovering  an  instance  of 
any  anomaly  it  is  therefore  impossible  to  tell 
whether  it  belongs  to  a  poor  or  to  a  rich  race. 
This  important  question  can  only  be  answered 
by  direct  sowing-experiments  to  determine  the 
degree  of  heredity. 

Monstrosities  are  often  considered  as  acci- 
dents, and  rightfully  so,  at  least  as  long  as  they 
are  considered  from  a  morphological  point  of 
view.  Physiology  of  course  excludes  all  acci- 
dentality.     And  in  our  present  case  it  shows 

400 


Monstrosities  401 

that  some  internal  hereditary  quality  is  pres- 
ent, though  often  latent,  and  that  the  observed 
anomalies  are  to  be  regarded  as  responses 
of  this  innate  tendency  to  external  con- 
ditions. Our  two  types  differ  in  the  frequency 
of  these  responses.  Eare  in  the  poor  race,  they 
are  numerous  in  the  rich  variety.  The  external 
conditions  being  the  same  for  both,  the  heredi- 
tary factor  must  be  different.  The  tendency  is 
weak  in  the  one  and  strong  in  the  other.  In 
both  cases,  according  to  my  experience,  it  may 
be  weakened  or  strengthened  by  selection  and 
by  treatment.  Often  to  a  very  remarkable  de- 
gree, but  not  so  far  as  to  transgress  the  limits 
between  the  two  races.  Such  transgression 
may  apparently  be  met  with  from  time  to  time, 
but  then  the  next  generation  generally  shows 
the  fallacy  of  the  conclusion,  as  it  returns  more 
or  less  directly  to  the  type  from  which  the  strain 
had  been  derived. 

Monstrosities  should  always  be  studied  by 
physiologists  from  this  point  of  view.  Poor 
and  rich  strains  of  the  same  anomaly  seem  at 
first  sight  to  be  so  nearly  allied  that  it  might  be 
thought  to  be  very  easy  to  change  the  one  into 
the  other.  Nevertheless  such  changes  are  not 
on  record,  and  although  I  have  made  several  at- 
tempts in  this  line,  I  never  succeeded  in  passing 
the  limit.    I  am  quite  convinced  that  sometime 


402  Ever-sporting  Varieties 

a  method  will  be  discovered  of  arbitrarily  pro- 
ducing such  conversions,  and  perhaps  the  easi- 
est way  to  attain  artificial  mutations  may  lie 
concealed  here.  But  as  yet  not  the  slightest  in- 
dication of  this  possibility  is  to  be  found,  save 
the  fallacious  conclusions  drawn  from  too 
superficial  observations. 

Unfortunately  the  poor  strains  are  not  very 
interesting.  Their  chance  of  producing  beauti- 
ful instances  of  the  anomaly  for  which  they  are 
cultivated  is  too  small.  Exceptions  to  this  rule 
are  only  afforded  by  those  curious  and  rare 
anomalies,  which  command  general  attention, 
and  of  which,  therefore,  instances  are  always 
welcome.  In  such  cases  they  are  searched  for 
with  perseverance,  and  the  fact  of  their  rarity 
impresses  itself  strongly  on  our  mind. 

Twisted  stems  are  selected  as  a  first  example. 
This  monstrosity,  called  biastrepsis^  consists  of 
strongly  marked  torsions  as  are  seen  in  many 
species  with  decussate  leaves,  though  as  a  rule 
it  is  very  rare.  Two  instances  are  the  most 
generally  known,  those  of  the  wild  valerian 
(Valeriana  officinalis)  and  those  of  cultivated 
and  wild  sorts  of  teasels  (Dipsacus  fiillonum,  D. 
sylvestris,  and  others).  Both  of  these  I  have 
cultivated  during  upwards  of  fifteen  years,  but 
with  contradictorv  results.  The  valerian  is  a 
perennial    herb,   multipljang   itself   yearly   by 


Monstrosities  403 

slender  rootstocks  or  runners  producing  at  their 
tips  new  rosettes  of  leaves  and  in  the  center  of 
these  the  flowering  stem.  My  original  plant 
has  since  been  propagated  in  this  manner,  and 
during  several  years  I  preserved  large  beds 
with  hundreds  of  stems,  in  others  I  was  com- 
pelled to  keep  my  culture  within  more  restricted 
limits.  This  plant  has  produced  twisted  stems 
of  the  curious  shape,  with  a  nearly  straight 
flag  of  leaves  on  one  side,  described  by  De  Can- 
dolle  and  other  observers,  nearly  every  year. 
But  only  one  or  two  instances  of  abnormal 
stems  occurred  in  each  year,  and  no  treatment 
has  been  found  that  proved  adequate  to  increase 
this  number  in  any  appreciable  manner.  I  have 
sown  the  seeds  of  this  plant  repeatedly,  either 
from  normal  or  from  twisted  stems,  but  without 
better  results.  It  was  highly  desirable  to  be 
able  to  offer  instances  of  this  rare  and  interest- 
ing peculiarity  to  other  universities  and  mxU- 
seums,  but  no  improvement  of  the  race  could  be 
reached  and  I  have  been  constrained  to  give  it 
up.  My  twisted  valerian  is  a  poor  race,  and 
hardly  anything  can  be  done  with  it.  Perhaps, 
in  other  countries  the  corresponding  rich  race 
may  be  hidden  somewhere,  but  I  have  never  had 
the  good  fortune  of  finding  it. 

This  good  fortune   however,  I  did  have  with 
the  wild  teasel  or  Bipsacus  sylvestris.    Twisted 


404  Ever-sporting  Varieties 

stems  of  this  and  of  allied  species  are  often  met 
with  and  have  been  described  by  several  writers, 
but  they  were  always  considered  as  acci- 
dents and  nobody  had  ever  tried  to  cultivate 
them.  In  the  summer  of  1885  I  saw  among  a 
lot  of  normal  wild  teasels,  two  nicely  twisted 
stems  in  the  botanical  garden  of  Amsterdam. 
I  at  once  proposed  to  ascertain  whether  they 
would  yield  a  hereditary  race  and  had  all  the 
normal  individuals  thrown  away  before  the 
flowering  time.  My  two  plants  flowered  in  this 
isolated  condition  and  were  richly  pollinated  by 
insects.  Of  course,  at  that  time,  I  knew  nothing 
of  the  dependency  of  monstrosities  on  external 
conditions,  and  made  the  mistake  of  sowing  the 
seeds  and  cultivating  the  next  generation  in 
too  great  numbers  on  a  small  space.  But 
nevertheless  the  anomaly  was  repeated,  and  the 
aberrant  individuals  were  once  more  isolated 
before  flowering.  The  third  generation  re- 
peated the  second,  but  produced  sixty  twisted 
stems  on  some  1600  individuals.  The  result 
was  very  striking  and  quite  sufficient  for  all  fur- 
ther researches,  but  the  normal  condition  of  the 
race  was  not  reached.  This  was  the  case  only 
after  I  had  discovered  the  bad  effects  of  grow- 
ing too  many  plants  in  a  limited  space.  In  the 
fourth  generation  I  restricted  my  whole  culture 
to  about  100  individuals,  and  by  this  simple 


Monstrosities  405 

means  at  once  got  up  to  34^  of  twisted  stems. 
This  proportion  has  since  remained  practically 
the  same.  I  have  selected  and  isolated  my 
plants  during  ^ye  succeeding  generations,  but 
without  any  further  result,  the  percentage  of 
twisted  stems  fluctuating  between  30  and 
about  45  according  to  the  size  of  the  cultures 
and  the  favorableness  or  unfavorableness  of  the 
weather. 

It  is  very  interesting  to  note  that  all  depends 
on  the  question  whether  one  has  the  good  for- 
tune of  finding  a  rich  race  or  not,  as  this  pedi- 
gree-culture shows.  Afterwards  everything  de- 
pends on  treatment  and  very  little  on  selection. 
As  soon  as  the  treatment  becomes  adequate,  the 
full  strength  of  the  race  at  once  displays  itself, 
but  afterwards  no  selection  is  able  to  improve 
it  to  any  appreciable  amount.  Of  course,  in 
the  long  run,  the  responses  will  be  the  same  as 
those  of  the  pistilloid  poppies  on  the  average, 
and  some  influence  of  selection  will  show  itself 
on  closer  scrutiny. 

Compared  with  the  polycephalous  poppies  my 
race  of  twisted  teasels  is  much  richer  in  atav- 
ists.  They  are  never  absent,  and  always  con- 
stitute a  large  part  of  each  generation  and  each 
bed,  comprising  somewhat  more  than  half  of  the 
individuals.  Intermediate  stages  between  them 
and  the  wholly  twisted  stems  are  not  wanting, 


406  Ever-sporting  Varieties 

and  a  whole  series  of  steps  may  easily  be  ob- 
served from  sufficiently  large  cultures.  But 
they  are  always  relatively  rare,  and  any  lot  of 
plants  conveys  the  idea  of  a  dimorphous  race, 
the  small  twisted  stems  contrasting  strongly 
with  the  tall  straight  ones. 

A  sharper  contrast  between  good  representa- 
tives of  a  race  and  their  atavists  is  perhaps  to 
be  seen  in  no  other  instance.  All  the  details 
contribute  to  the  differentiation  in  appearance. 
The  whole  stature  of  the  plants  is  affected  by 
the  varietal  mark.  The  atavists  are  not,  as 
in  the  case  of  the  poppies,  obviously  allied  with 
the  type  by  a  full  range  of  intermediate  steps, 
but  quite  distant  from  it  by  their  rarity.  There 
seems  to  be  a  gap  in  the  same  way  as  between 
the  striped  flowers  of  the  snapdragon  and  their 
uniform  red  atavists,  while  with  the  poppies 
the  atavists  may  be  viewed  as  being  only  the 
extremes  of  a  series  of  variations  fluctuating 
around  some  average  type. 

From  this  reason  it  is  as  interesting  to  appre- 
ciate the  hereditary  position  of  the  atavists  of 
twisted  varieties  as  it  was  for  the  red-flowered 
descendants  of  the  striped  flowers.  In  order  to 
ascertain  this  relation  it  is  only  necessary  to  iso- 
late some  of  them  during  the  blooming-period. 
I  made  this  experiment  in  the  summer  of  1900 
with  the  eighth  generation  of  my  race,  and  con- 


Monstrosities  407 

trived  to  isolate  three  groups  of  plants  by  the 
use  of  parchment  bags,  covering  them  alter- 
nately, so  the  flowers  of  only  one  group  were 
accessible  to  insects  at  a  time.  I  made  three 
groups,  because  the  atavists  show  two  different 
types.  Some  specimens  have  decussate  stems, 
others  bear  all  their  leaves  in  whorls  of  three, 
but  in  respect  to  the  hereditary  tendency  of  the 
twisting  character  this  difference  does  not  seem 
to  be  of  any  importance. 

In  this  way  I  got  three  lots  of  seeds  and  sowed 
enough  of  them  to  have  three  groups  of  plants 
each  containing  about  150  -  200  well  developed 
stems.  Among  these  I  counted  the  twisted  indi- 
viduals, and  found  nearly  the  same  numbers  for 
all  three.  The  twisted  parents  gave  as  many 
as  4rlfc  twisted  children,  but  the  decussate  ata- 
vists gave  even  somewhat  more,  viz.,  44;^,  while 
the  ternate  specimens  gave  37;^.  Obviously  the 
divergencies  between  these  figures  are  too  slight 
to  be  dwelt  upon,  but  the  fact  that  the  atavists 
are  as  true  or  nearly  as  true  inheritors  of  the 
twisted  race  as  the  best  selected  individuals  is 
clearly  proved  by  this  experience. 

It  is  evident  that  here  we  have  a  double  race, 
including  two  types,  which  may  be  combined  in 
different  degrees.  These  combinations  deter- 
mine a  wide  range  of  changes  in  the  stature  of 
the  plants,  and  it  seems  hardly  right  to  use  the 


408  Ever-sporting  Varieties 

same  term  for  such  changes  as  for  common 
variations.  It  is  more  a  contention  of  opposite 
characters  than  a  true  phenomenon  of  simple 
variability.  Or  perhaps  we  might  say  that  it 
is  the  effect  of  the  cooperation  of  a  very  vari- 
able mark,  the  twisting,  with  a  scarcely  varying 
attribute  of  the  normal  structure  of  the  stem. 
Between  the  two  types  an  endless  diversity  pre- 
vails, but  outwardly  there  are  limits  which  are 
never  transgressed.  The  double  race  is  as  per- 
manent, and  in  this  sense  as  constant,  as  any 
ordinary  simple  variety,  both  in  external  form, 
and  in  its  intimate  hereditary  qualities. 

I  have  succeeded  in  discovering  some  other 
rich  races  of  twisted  plants.  One  of  them 
is  the  Sweet  William  {Dianthus  harhatus), 
which  yielded,  after  isolation,  in  the  second 
generation,  25^  of  individuals  with  twisted 
stems,  and  as  each  individual  produces  often 
10  and  more  stems,  I  had  a  harvest  of 
more  than  half  a  thousand  of  instances  of  this 
curious,  and  ordinarily  very  rare  anomaly.  My 
other  race  is  a  twisted  variety  of  Viscaria  ocula- 
ta,  which  is  still  in  cultivation,  as  it  has  the  very 
consistent  quality  of  being  an  annual.  It  yield- 
ed last  summer  (1903)  as  high  a  percentage  as 
65  of  twisted  individuals,  many  of  them  repeat- 
ing the  monstrosity  on  several  branches.  After 
some  occasional  observations  Gypsophila  pani- 


Monstrosities  409 

culata  seems  to  promise  similar  results.  On 
the  other  hand  I  have  sowed  in  vain  the  seeds  of 
twisted  specimens  of  the  soapwort  and  the 
cleavewort  (Saponaria  officinalis  and  Galium 
Aparine).  These  and  some  others  seems  to  be- 
long to  the  same  group  as  the  valerian  and  to 
constitute  only  poor  or  so-called  half -races. 

Next  to  the  torsions  come  the  fasciated 
stems.  This  is  one  of  the  most  common  of  all 
malformations,  and  consists,  in  its  ordinary 
form,  of  a  flat  ribbon-like  expansion  of  the  stems 
or  branches.  Below  they  are  cylindrical,  but 
they  gradually  lose  this  form  and  assume  a  flat- 
tened condition.  Sometimes  the  rate  of  growth 
is  unequal  on  different  portions  or  on  the  op- 
posite sides  of  the  ribbon,  and  curvatures  are 
produced  and  these  often  give  to  the  fasciation 
a  form  that  might  be  compared  with  a  shep- 
herd's crook.  It  is  a  common  thing  for  fas- 
ciated branches  and  stems  to  divide  at  the 
summit  into  a  number  of  subdivisions,  and  ordi- 
narily this  splitting  occurs  in  the  lower  part, 
sometimes  dividing  the  entire  fasciated  portion. 
In  biennial  species  the  rosette  of  the  root-leaves 
of  the  first  year  may  become  changed  by  the 
monstrosity,  the  heart  stretching  in  a  transverse 
direction  so  as  to  become  linear.  In  the  next 
year  this  line  becomes  the  base  from  which  the 
stem  grows.    In  such  cases  the  fasciated  stems 


410  Ever-sporting  Varieties 

are  broadened  and  flattened  from  the  very  be- 
ginning, and  often  retain  the  incipient  breadth 
throughout  their  further  development.  Species 
of  primroses  {Primula  japonica  and  others),  of 
buttercups  {Ranunculus  bulbosus),  the  rough 
hawksbeard  {Crepis  biennis),  the  Aster  Tripo- 
lium  and  many  others  could  be  given  as  in- 
stances. 

Some  of  these  are  so  rare  as  to  be  considered 
as  poor  races,  and  in  cultural  trials  do  not  pro- 
duce the  anomaly  except  in  a  very  few  in- 
stances. Heads  of  rye  are  found  in  a  cleft 
condition  from  time  to  time,  single  at  their  base 
and  double  at  the  top,  but  this  anomaly  is  only 
exceptionally  repeated  from  seed.  Flattened 
stems  of  Rubia  tinctorum  are  not  unfrequently 
met  with  on  the  fields,  but  they  seem  to  have  as 
little  hereditary  tendency  as  the  split  rye 
{Secale  Cereale).  Many  other  instances  could 
be  given.  Both  in  the  native  localities  and  in 
pedigree-cultures  such  ribboned  stems  are  only 
seen  from  time  to  time,  in  successive  years,  in 
annual  and  biennial  as  well  as  in  perennial 
species.  The  purple  pedicularis  {Pedicularis 
palustris)  in  the  wild  state,  and  the  sunflower 
among  cultivated  plants,  may  be  cited  instead  of 
giving  a  long  list  of  analogous  instances. 

On  the  other  hand  rich  races  of  flattened 
stems  are  not  entirely  lacking.     They  easily  be- 


Monstrosities  411 

tray  themselves  by  the  frequency  of  the  anom- 
aly, and  therefore  may  be  found,  and  tried  in 
the  garden.  Under  adequate  cultivation  they 
are  here  as  rich  in  aberrant  individuals  as  the 
twisted  races  quoted  above,  producing  in  good 
years  from  30  -  4:0^  and  often  more  instances.  I 
have  cultivated  such  rich  races  of  the  dandelion 
(Taraxacum  officinale) ^  of  Thrincia  hirta,  of  the 
dame's  violet  (Hesperis  matronalis),  of  the 
hawkweed  (Picris  hieracioides) ,  of  the  rough 
hawksbeard  (Crepis  biennis),  and  others. 

Respecting  the  hereditary  tendencies  these 
rich  varieties  with  flattened  stems  may  be  put  in 
the  same  category  with  the  twisted  races.  Two 
points  however,  seem  to  be  of  especial  interest 
and  to  deserve  a  separate  treatment. 

The  common  cockscomb  or  Celosia  cristata, 
one  of  the  oldest  and  most  widely  cultivated 
fasciated  varieties  may  be  used  to  illustrate 
the  first  point.  In  beds  it  is  often  to  be; 
seen  in  quite  uniform  lots  of  large  and  beau- 
tiful crests,  but  this  uniformity  is  only  se- 
cured by  careful  culture  and  selection  of  the 
best  individuals.  In  experimental  trials 
such  selection  must  be  avoided,  and  in  doing 
so  a  wide  range  of  variability  at  once  shows 
itself.  Tall,  branched  stems  with  fan- 
shaped  tops  arise,  constituting  a  series  of 
steps    towards    complete    atavism.     This    last 


412  Ever-sporting  Varieties 

however,  is  not  to  be  reached  easily.  It  often 
requires  several  successive  generations  grown 
from  seed  collected  from  the  most  atavistic  spec- 
imens. And  even  such  selected  strains  are  al- 
ways reverting  to  the  crested  type.  There  is 
no  transgression,  no  springing  over  into  a 
purely  atavistic  form,  such  as  may  be  supposed 
to  have  once  been  the  ancestor  of  the  present 
cockscomb.  The  variety  includes  crests  and 
atavists,  and  may  be  perpetuated  from  both. 
Obviously  every  gardener  would  select  the  seeds 
of  the  brightest  crests,  but  with  care  the  full 
crests  may  be  recovered,  even  from  the  worst 
reversionists  in  two  or  three  generations.  It  is 
a  double  race  of  quite  the  same  constitution  as 
the  twisted  teasels. 

My  second  point  is  a  direct  proof  of  this  as- 
sertion, but  made  with  a  fasciated  variety  of  a 
wild  species.  I  took  for  my  experiment  the 
rough  hawksbeard.  In  the  summer  of  1895  I 
isolated  some  atavists  of  the  fifth  generation  of 
my  race,  which,  by  ordinary  selection,  gave  in 
the  average  from  20-40^  of  fasciated  stems. 
My  isolated  atavists  bore  abundant  fruit,  and 
from  these  I  had  the  next  year  a  set  of  some  350 
plants,  out  of  which  about  20^  had  broadened 
and  linear  rosettes.  This  proportion  corre- 
sponds with  the  degree  of  inheritance  which  is 
shown  in  many  years  by  the  largest  and  strong- 


Monstrosities  413 

est  fasciated  stems.  It  strengthens  our  conclu- 
sion as  to  the  innermost  constitution  of  the 
double  races  or  ever-sporting  varieties. 

Twisted  stems  and  fasciations  are  very  strik- 
ing monstrosities.  But  they  are  not  very  good 
for  further  investigation.  They  require  too 
much  space  and  too  much  care.  The  calculation 
of  a  single  percentage  requires  the  counting  of 
some  hundreds  of  individuals,  taking  many 
square  meters  for  their  cultivation,  and  this,  as 
my  best  races  are  biennial,  during  two  years. 
For  this  reason  the  countings  must  always  be 
very  limited,  and  selection  is  restrained  to  the 
most  perfect  specimens. 

Now  the  question  arises,  whether  this  mark 
is  the  best  upon  which  to  found  selection.  This 
seems  to  be  quite  doubtful.  In  the  experiments 
on  the  heredity  of  the  atavists,  we  have  seen 
that  they  are,  at  least  often,  in  no  manner 
inferior  to  even  the  best  inheritors  of  the  race. 
This  suggests  the  idea  that  it  is  not  at  all  certain 
that  the  visible  characters  of  a  given  individual 
are  a  trustworthy  measure  of  its  value  as  to  the 
transmission  of  the  same  character  to  the  off- 
spring. In  other  words,  we  are  confronted  with 
the  existence  of  two  widely  different  groups  of 
characters  in  estimating  the  hereditary  tend- 
ency. One  is  the  visible  quality  of  the  indi- 
viduals and  the  other  is  the  direct  observation 


414  Ever-sporting  Varieties 

of  the  degree  in  which  the  attribute  is  trans- 
mitted. These  are  by  no  means  parallel,  and 
seem  in  some  sense  to  be  nearly  independent 
of  each  other.  The  fact  that  the  worst  atavists 
may  have  the  highest  percentage  of  varietal 
units  seems  to  leave  no  room  for  another  ex- 
planation. 

Developing  this  line  of  thought,  we  gradually 
arrive  at  the  conclusion  that  the  visible  attribute 
of  a  varying  individual  is  perhaps  the  most  un- 
trustworthy and  the  most  unreliable  character 
for  selection,  even  if  it  seems  in  many  cases 
practically  to  be  the  only  available  one.  The  di- 
rect determination  of  the  degree  of  heredity  it- 
self is  obviously  preferable  by  far.  This  degree 
is  expressed  by  the  proportion  of  its  inheritors 
among  the  offspring,  and  this  figure  therefore 
should  be  elevated  to  the  highest  rank,  as  a 
measure  of  the  hereditary  qualities.  Hence- 
forward we  will  designate  it  by  the  name  of 
hereditary  percentage. 

In  scientific  experiments  this  figure  must  be 
determined  for  every  plant  of  a  pedigree-culture 
singly,  and  the  selection  should  be  founded  ex- 
clusively or  at  least  mainly  on  it.  It  is  easily 
seen  that  this  method  requires  large  numbers 
of  individuals  to  be  grown  and  counted.  Some 
two  or  three  hundred  progeny  of  one  plant  are 
needed  to  give  the  decisive  figure  for  this  one 


Monstrosities  415 

individual,  and  selection  requires  the  compari- 
son of  at  least  fifty  or  more  individuals.  This 
brings  the  total  amount  of  specimens  to  be 
counted  up  to  some  tens  of  thousands.  In  prac- 
tice, where  important  interests  depend  upon  the 
experiments,  such  numbers  are  usually  em- 
ployed and  often  exceeded,  but  for  the  culture 
of  monstrosities,  other  methods  are  to  be  sought 
in  order  to  avoid  these  difficulties. 

The  idea  suggests  itself  here  that  the  younger 
the  plants  are,  when  showing  their  distinguish- 
ing marks,  the  more  of  them  may  be  grown  on  a 
small  space.  Hence  the  best  way  is  to  choose 
such  attributes,  as  may  already  be  seen  in  the 
young  seedlings,  in  the  very  first  few  weeks  of 
their  lives.  Fortunately  the  seed-leaves  them- 
selves afford  such  distinctive  marks,  and  by  this 
means  the  plants  may  be  counted  in  the 
pans,  requiring  no  culture  at  all  in  the  gar- 
den. Only  the  selected  individuals  need  be 
grown  to  ripen  their  seeds,  and  the  whole  selec- 
tion may  be  made  in  the  spring,  in  the  glass- 
house. Instead  of  being  very  troublesome,  the 
determination  of  the  hereditary  percentages 
becomes  a  definite  reduction  of  the  size  of  the 
experiments.  Moreover  it  may  easily  be  effect- 
ed by  any  one  who  cares  for  experimental 
studies,  but  has  not  the  means  required  for  cul- 
tures on  a  larger  scale.     i\nd  lastly,  there  are 


416  Ever-sporting  Varieties 

a  number  of  questions  about  heredity,  period- 
icity, dependency  on  nourishment  and  other  life- 
conditions,  and  even  about  hybridizing,  which 
may  be  answered  by  this  new  method. 

Seed-leaves  show  many  deviations  from  the 
ordinary  shape,  especially  in  dicotyledonous 
plants.  A  very  common  aberration  is  the  multi- 
plication of  their  number,  and  three  seed-leaves 
in  a  whorl  are  not  rarely  met  with.  The  whorl 
may  even  consist  of  four,  and  in  rare  cases  of 
five  or  more  cotyledons.  Cleft  cotyledons  are 
also  to  be  met  with,  and  the  fissure  may  extend 
varying  distances  from  the  tips.  Often  all  these 
deviations  may  be  seen  among  the  seedlings 
of  one  lot,  and  then  it  is  obvious  that  together 
they  constitute  a  scale  of  cleavages,  the  ternate 
and  quaternate  whorls  being  only  cases  where 
the  cleaving  has  reached  its  greatest  develop- 
ment. All  in  all  it  is  manifest  that  here  we  are 
met  by  one  type  of  monstrosity,  but  that  this 
type  allows  of  a  wide  range  of  fluctuating  varia- 
bility. For  brevity's  sake  all  these  cleft  and 
ternate,  double  cleft  and  quaternate  cotyledons 
and  even  the  higher  grades  are  combined  under 
one  common  name  and  indicated  as  tricotyls. 

A  second  aberration  of  young  seed-plants  is 
exactly  opposite  to  this.  It  consists  of  the 
union  of  the  two  seed-leaves  into  a  single 
organ.     This  ordinarily  betrays  its  origin  by 


Monstrosities  417 

having  two  separate  apices,  but  not  always, 
Such  seedlings  are  called  syncotyledonous  or 
syncotyls.  Other  monstrosities  have  been  ob- 
served from  time  to  time,  but  need  not  be  men- 
tioned here. 

It  is  evident  that  the  determination  of  the 
hereditary  percentage  is  very  easy  in  tricotyl- 
ous  or  syncotylous  cultures.  The  parent- 
plants  must  be  carefully  isolated  while  bloom- 
ing. Many  species  pollinate  themselves  in  the 
absence  of  bees;  from  these  the  insects  are 
to  be  excluded.  Others  have  the  stamens  and 
stigmas  widely  separated  and  have  to  be  polli- 
nated artificially.  Still  others  do  not  lend  them- 
selves to  such  operations,  but  have  to  be  left  free 
to  the  visits  of  bees  and  of  humble-bees,  this  be- 
ing the  only  means  of  securing  seed  from  every 
plant.  At  the  time  of  the  harvest  the  seeds 
should  be  gathered  separately  from  each  plant, 
and  this  precaution  should  also  be  observed  m 
studies  of  the  hereditary  percentage  at  large, 
and  in  all  scientific  pedigree-cultures.  Every  lot 
of  seeds  is  to  be  sown  in  a  separate  pan,  and  care 
must  be  taken  to  sow  such  quantities  that  three 
to  four  hundred  seedlings  will  arise  from  each. 
As  soon  as  they  display  their  cotyledons,  they 
are  counted,  and  the  number  is  the  criterion  of 
the  parent-plant.  Only  parent-plants  with  the 
highest  percentages  are  selected,  and  out  of 


418  Ever-sporting  Varieties 

their  seedlings  some  fifty  or  a  hundred  of  the 
best  ones  are  chosen  to  furnish  the  seeds  for  the 
next  generation. 

This  description  of  the  method  shows  that 
the  selection  is  a  double  one.  The  first  feature 
is  the  hereditary  percentage.  But  then  not  all 
the  seedlings  of  the  selected  parents  can  be 
planted  out,  and  a  choice  has  to  be  made.  This 
second  selection  may  favor  the  finest  tricotyls, 
or  the  strongest  individuals,  or  rely  on  some 
other  character,  but  is  unavoidable. 

We  now  come  to  the  description  of  the  cul- 
tures. Starting  points  are  the  stray  tricotyls 
which  are  occasionally  found  in  ordinary 
sowings.  In  order  to  increase  the  chance  of 
finding  them,  thousands  of  seeds  of  the  same 
species  must  be  inspected,  and  the  range  of 
species  must  be  widened  as  much  as  possible. 

Material  for  beginning  such  experiments  is 
very  easily  obtained,  and  almost  any  large 
sample  of  seeds  will  be  found  suitable.  Some 
tricotyls  may  be  found  among  every  thousand 
seedlings  in  many  species,  while  in  others  ten  or 
a  hundred  times  as  many  plants  must  be  exam- 
ined to  secure  them,  but  species  with  absolutely 
pure  dicotylous  seeds  are  very  rare. 

The  second  phase  of  the  experiment  how- 
ever, is  not  so  promising.  Some  species  are  rich, 
and  others  are  poor  in  this  anomaly.     This  dif- 


Monstrosities  419 

ference  often  indicates  what  may  be  expected 
from  further  culture.  Stray  tricotyls  point  to 
poor  or  half-races,  while  more  frequent  devia- 
tions suggest  rich  or  double-races.  In  both 
cases  however,  the  trial  must  be  made,  and  this 
requires  the  isolation  of  the  aberrant  individ- 
uals and  the  determination  of  their  hereditary 
percentage. 

In  some  instances  the  degree  of  their  in- 
heritance is  only  a  very  small  one.  The  iso- 
lated tricotyls  yield  1  or  2fo  of  inheritors,  in  some 
cases  even  less,  or  upwards  to  3  or  4^.  If  the 
experiment  is  repeated,  no  amelioration  is  ob- 
served, and  this  result  remains  the  same  during 
a  series  of  successive  generations.  In  the  case 
of  Polygonum  Convolvulus,  the  black  bindweed, 
I  have  tried  as  many  as  six  generations  without 
ever  obtaining  more  than  3^.  With  other 
species  I  have  limited  myself  to  four  successive 
years  with  the  same  negative  result,  as  with 
spinage,  the  Moldavian  dragon-head  {Dracoce- 
phalum  moldavicum),  and  two  species  of  corn 
catch-fly  (Silene  conica  and  8.  conoidea). 

Such  poor  races  hardly  afford  a  desirable  ma- 
terial for  further  inquiries.  Happily  the  rich 
races,  though  rare,  may  be  discovered  also  from 
time  to  time.  They  seem  to  be  more  common 
among  cultivated  plants  and  horticultural  as 
well  as  agricultural  species  may  be  used.     Henq) 


420  Ever-sporting  Varieties 

and  mercury  (Mercurialis  annua)  among  the 
first,  snapdragon,  poppies,  Phacelia,  Helich- 
rysuyn,  and  Clarkia  among  garden-flowers  may 
be  given  as  instances  of  species  containing  the 
rich  tricotylous  double  races. 

It  is  very  interesting  to  note  how  strong  the 
difference  is  between  such  cases  and  those  which 
only  yield  poor  races.  The  rich  type  at  once 
betrays  itself.  No  repeated  selection  is  re- 
quired. The  stray  tricotyls  themselves,  that 
are  sought  out  from  among  the  original  samples, 
give  hereditary  percentages  of  a  much  higher 
type  after  isolation  than  those  quoted  above. 
They  come  up  to  10  -  20^  and  in  some  cases  even 
to  40^.  As  may  be  expected,  individual  differ- 
ences occur,  and  it  must  even  be  supposed  that 
some  of  the  original  tricotyls  may  not  be  pure, 
but  hybrids  between  tricotylous  and  dicotyl- 
ous  parents.  These  are  at  once  eliminated 
by  selection,  and  if  only  the  tricotyls  which 
have  the  highest  percentages  are  chosen  for  the 
continuance  of  the  new  race,  the  second  genera- 
tion comes  up  with  equal  numbers  of  dicotyls 
and  tricotyls  among  the  seedlings.  The  figures 
have  been  observed  to  range  from  51  -  58^  in  the 
majority  of  the  cases,  and  average  55^,  rarely 
diverging  somewhat  more  from  this  average. 

Here  we  have  the  true  type  of  an  ever-sport- 
ing variety.    Every  year  it  produces  in  the 


Monstrosities  421 

same  way  heirs  and  atavists.  Every  plant,  if 
fertilized  with  its  own  pollen,  gives  rise  to 
both  types.  The  parent  itself  may  be  tricotyl- 
ous  or  dicotylous,  or  show  any  amount  of 
multiplication  and  cleavage  in  its  seed-leaves, 
but  it  always  gives  the  entire  range  among  its 
progeny  of  the  variation.  One  may  even  select 
the  atavists,  pollinate  them  purely  and  repeat 
this  in  a  succeeding  generation  without  any 
chance  of  changing  the  result.  On  an  average 
the  atavists  may  give  lower  hereditary  figures, 
but  the  difference  will  be  only  slight. 

Such  tricotylous  double  races  offer  highly 
interesting  material  for  inquiries  into  questions 
of  heredity,  as  they  have  such  a  wide  range  of 
variability.  There  is  little  danger  in  asserting 
that  they  go  upwards  to  nearly  100^,  and  down- 
wards to  Ofo^  diverging  symmetrically  on  both 
sides  of  their  average  (50-55;'^).  These  limits 
they  obviously  cannot  transgress,  and  are  not 
even  able  to  reach  them.  Samples  of  seed  con- 
sisting only  of  tricotyls  are  very  rare,  and  when 
they  are  met  with  the  presumption  is  that  they 
are  too  few  to  betray  the  rare  aberrants  they 
might  otherwise  contain.  Experimental  evi- 
dence can  only  be  reached  by  the  culture  of  a 
succeeding  generation,  and  this  always  discloses 
the  hidden  qualities,  showing  that  the  double 


422  Ever-sporting  Varieties 

type  was  only  temporarily  lost,  but  bound  to 
return  as  soon  as  new  trials  are  made. 

This  wide  range  of  variability  between  def- 
inite limits  is  coupled  with  a  high  degree  of 
sensibility  and  adequateness  to  the  most  di- 
verging experiments.  Our  tricotylous  double 
races  are  perhaps  more  sensitive  to  selection 
than  any  other  variety,  and  equally  dependent 
on  outer  circumstances.  Here,  however,  I  will 
limit  myself  to  a  discussion  of  the  former  point. 

In  the  second  generation  after  the  isolation  of 
stray  tricotylous  seedlings  the  average  con- 
dition of  the  race  is  usually  reached,  but  only 
by  some  of  the  strongest  individuals,  and  if  we 
continue  the  race,  sowing  or  planting  only  from 
their  offspring,  the  next  generation  will  show 
the  ordinary  type  of  variability,  going  upwards 
in  some  and  downwards  in  other  instances. 
With  the  Phacelia  and  the  mercury  and  some 
others  I  had  the  good  luck  in  this  one  generation 
to  reach  as  high  as  nearly  90;^  of  tricotyl- 
ous seedlings,  a  figure  indicating  that  the 
normal  dicotylous  type  had  already  become 
rare  in  the  race.  In  other  cases  80^  or 
nearly  80^  was  easily  attained.  Any  further 
divergence  from  the  average  would  have  re- 
quired very  much  larger  sowings,  the  effect  of 
selection  between  a  limited  number  of  parents 
being   only   to    retain    the    high    degree    once 


Monstrosities  423 

reached ;  so  for  instance  with  the  mercury,  I  had 
three  succeeding  generations  of  selection  after 
reaching  the  average  of  55;^,  but  their  extremes 
gave  no  increasing  advance,  remaining  at  86,  92 
and  91^. 

If  we  compare  these  results  with  the  effects 
of  selection  in  twisted  and  fasciated  races,  we 
observe  a  marked  contrast.  Here  they  reached 
their  height  at  30-40%,  and  no  number  of  gen- 
erations had  the  power  of  making  any  further 
improvement.  The  tricotyls  come  up  in  two 
generations  to  a  proportion  of  about  54;^,  which 
shows  itself  to  correspond  to  the  average 
type.  And  as  soon  as  this  is  reached,  only  one 
generation  is  required  to  obtain  a  very  consid- 
erable improvement,  going  up  to  80  or  even  90;?^. 

It  is  evident  that  the  cause  of  this  difference 
does  not  lie  in  the  nature  of  the  monstrosity,  but 
is  due  to  the  criterion  upon  which  the  selection 
is  made.  Selection  of  the  apparently  best  in- 
dividuals is  one  method,  and  it  gives  admirable 
results.  Selection  on  the  ground  of  the  hered- 
itary percentages  is  another  method  and  gives 
results  which  are  far  more  advantageous  than 
the  former. 

In  the  lecture  on  the  pistillody  of  the  poppies 
we  limited  ourselves  to  the  selection  of  the  finest 
individuals  and  showed  that  there  is  always  a 
manifest    correlation    between    the    individual 


424  Ever-sporting  Varieties 

strength  of  the  plant  and  the  degree  of  develop- 
ment of  its  anomaly.  The  same  holds  good  with 
other  monstrosities,  and  badly  nourished  speci- 
mens of  rich  races  with  twisted  or  fasciated 
stems  always  tend  to  reversion.  This  rever- 
sion, however,  is  not  necessarily  correlated  with 
the  hereditary  percentage  and  therefore  does 
not  always  indicate  a  lessening  of  the  degree  of 
inheritance.  This  shows  that  even  in  those 
cases  an  improvement  may  be  expected,  if  only 
the  means  can  be  found  to  subject  the  twisted 
and  the  fasciated  races  to  the  same  sharp  test 
as  the  tricotylous  varieties. 

Much  remains  to  be  done,  and  the  principle  of 
the  selection  of  parents  according  to  the  average 
constitution  of  their  progeny  seems  to  be  one  of 
the  most  promising  in  the  whole  realm  of  varia- 
bility. 

Besides  tricotylous,  the  syncotylous  seed- 
lings may  be  used  in  the  same  way.  They 
are  more  rarely  met  with,  ind  in  most  instances 
seem  to  belong  only  to  the  unpromising  half- 
races.  The  black  bindweed  {Polygonum  Con- 
volvulus), the  jointed  charlock  {Raplianus  Uap- 
hanistrum),  the  glaucous  evpniug-prir  irose 
{Oenothera  glauca)  and  many  other  plants  seem 
to  contain  such  half-rac^s.  On  the  other  hand 
I  found  a  plant  of  Centrantlms  macrosiphon 
yielding  as  much  as  55;^  of  syncotylous  chil- 


Monstrosities  425 

dren  and  thereby  evidently  betraying  the  na- 
ture of  a  rich  or  double  race.  Likewise  the  mer- 
cury was  rich  in  such  deviations.  But  the  best 
of  all  was  the  Russian  sunflower,  and  this  was 
chosen  for  closer  experiments. 

In  the  year  of  1888  I  had  the  good  luck  to 
isolate  some  syncotylous  seedlings  and  of  find- 
ing among  them  one  with  19^  of  inheritors 
among  its  seeds.  The  following  generation  at 
once  surpassed  the  ordinary  average  and  came 
up  in  three  individuals  to  76,  81  and  even  89^. 
My  race  was  at  once  isolated  and  ameliorated  by 
selection.  I  have  tried  to  improve  it  further 
and  selected  the  parents  with  the  highest  per- 
centages during  seven  more  generations;  but 
without  any  remarkable  result.  I  got  figures  of 
90^  and  above,  coming  even  in  one  instance  up 
to  the  apparent  purity  of  100^.  These,  how- 
ever, always  remained  extremes,  the  averages 
fluctuating  yearly  between  80-90,*^  or  there- 
abouts, and  the  other  extremes  going  nearly 
every  year  downwards  to  50^,  the  value  which 
would  be  attained,  if  no  selection  were  made. 

Contra-selection  is  as  easily  made  as  normal 
selection.  According  to  our  present  principle  it 
means  the  choice  of  the  parents  with  the  smallest 
hereditary  percentage.  One  might  easily  im- 
agine that  by  this  means  the  dicotylous  seed- 
lings   could    be    rendered    pure.     This,    how- 


426  Ever-sporting  ]^arieties 

ever,  is  not  at  all  the  case.  It  is  easy  to  re- 
turn from  so  highly  selected  figures  as  for  in- 
stance 9^^  to  the  average  about  of  50^,  as 
regression  to  mediocrity  is  always  an  easy  mat- 
ter. But  to  transgress  this  average  on  the 
lower  side  seems  to  be  as  difficult  as  it  is  on  the 
upper  side.  I  continued  the  experiment  during 
four  succeeding  generations,  but  was  not  able  to 
go  lower  than  about  10/^,  and  could  not  even  ex- 
clude the  high  figures  from  my  strain.  Parents 
with  65  -  75^  of  syncotylous  seedlings  returned 
in  each  generation,  notwithstanding  the  most 
careful  contra-selection.  The  attribute  is  in- 
herent in  the  race,  and  is  not  to  be  eliminated  by 
so  simple  a  means  as  selection,  nor  even  by  a  se- 
lection on  the  ground  of  hereditary  percentages. 

We  have  dealt  with  torsions  and  fasciations 
and  with  seedling  variations  at  some  length,  in 
order  to  point  out  the  phases  needing  investiga- 
tion according  to  recent  views.  It  would  be 
quite  superfluous  to  consider  other  anomalies  in 
a  similar  manner,  as  they  all  obey  the  same  laws. 
A  hasty  survey  may  suffice  to  show  what  pros- 
pects they  offer  to  the  student  of  nature. 

First  of  all  come  the  variegated  leaves.  They 
are  perhaps  the  most  variable  of  all  variations. 
They  are  evidently  dependent  on  external  cir- 
cumstances, and  by  adequate  nutrition  the 
leaves  may  even  become  absolutely  white  or 


Monstrosities  427 

yellowish,  with  only  scarcely  perceptible  traces 
of  green  along  the  veins.  Some  are  very  old 
cultivated  varieties,  as  the  wintercress,  or  Bar- 
barea  vulgaris.  They  continuously  sport  into 
green,  or  return  from  this  normal  color,  both  by 
seeds  and  by  buds.  Sports  of  this  kind  are 
very  often  seen  on  shrubs  or  low  trees,  and 
they  may  remain  there  and  develop  during  a 
long  series  of  years.  Bud-sports  of  variegated 
holly,  elms,  chestnuts,  beeches  and  others  might 
be  cited.  One-sided  variegation  on  leaves  or 
twigs  with  the  opposite  side  wholly  green  are 
by  no  means  rare.  It  is  very  curious  to  note 
that  variegation  is  perhaps  the  most  universally 
known  anomalv,  while  its  hereditarv  tendencies 
are  least  known. 

Cristate  and  plumose  ferns  are  another  in- 
stance. Half  races  or  rare  accidental  cleavages 
seem  to  be  as  common  with  ferns  as  cultivated 
double  races,  which  are  very  rich  in  beautiful 
crests.  But  much  depends  on  cultivation.  It 
seems  that  the  spores  of  crested  leaves  are  more 
apt  to  reproduce  the  variety  than  those  of  nor- 
mal leaves,  or  even  of  normal  parts  of  the  same 
leaves.  But  the  experiments  on  which 
this  assertion  is  made  are  old  and  should 
be  repeated.  Other  cases  of  cleft  leaves  should 
also  be  tested.  Ascidia  are  far  more  common 
than  is  usually  believed.     Rare  instances  point 


428  Ever-sporting  Varieties 

to  poor  races,  but  the  magnolias  and  lime-trees 
are  often  so  productive  of  ascidia  as  to  suggest 
the  idea  of  ever-sporting  varieties.  I  have 
seen  many  hundred  ascidia  on  one  lime-tree,  and 
far  above  a  hundred  on  the  magnolia.  They  dif- 
fer widely  in  size  and  shape,  including  in  some 
cases  two  leaves  instead  of  one,  or  are  composed 
of  only  half  a  leaf  or  of  even  still  a  smaller  part 
of  the  summit.  Kich  ascidia-bearing  varieties 
seem  to  offer  notable  opportunities  for  scientific 
pedigree-cultures. 

Union  of  the  neighboring  fruits  and  flowers  on 
flower-heads,  of  the  rays  of  the  umbellifers  or 
of  the  successive  flowers  of  the  racemes  of  cab- 
bages and  allied  genera,  seem  to  be  rare. 
The  same  holds  good  for  the  adhesion  of  foliar 
to  axial  organs,  of  branches  to  stems  and 
other  cases  of  union.  Many  of  these  cases  re- 
turn regularly  in  each  generation,  or  may  at 
least  be  seen  from  time  to  time  in  the  same 
strains.  Proliferation  of  the  inflorescence  is 
very  common  and  changes  in  the  position  of 
staminate  and  pistillate  flowers  are  not  rare. 
We  find  starting  points  for  new  investigations 
in  almost  any  teratological  structure.  Half- 
races  and  double-races  are  to  be  distinguished 
and  isolated  in  all  cases,  and  their  hereditary 
qualities,  the  periodicity  of  the  recurrence  of 
the  anomaly,  the  dependency  on  external  circum- 


Monstrosities  429 

stances  and  many  other  questions  have  to  be  an- 
swered. 

Here  is  a  wide  field  for  garden  experiments 
easily  made,  which  might  ultimately  yield  much 
valuable  information  on  many  questions  of  he- 
redity of  universal  interest. 


Lecture  XV 

DOUBLE    ADAPTATIONS 

The  chief  object  of  all  experimentation  is  to 
obtain  explanations  of  natural  phenomena. 
Experiments  are  a  repetition  of  things  occur- 
ring in  nature  with  the  conditions  so  guarded 
and  so  closely  followed  that  it  is  possible  to 
make  a  clear  analysis  of  facts  and  their 
causes,  it  being  rightfully  assumed  that  the  laws 
are  the  same  in  both  cases. 

Experiments  on  heredity  and  the  experience 
of  the  breeder  find  their  analogy  in  the  succes- 
sion of  generations  in  the  wild  state.  The  sta- 
bility of  elementary  species  and  of  retrograde 
varieties  is  quite  the  same  under  both  condi- 
tions. Progression  and  retrogression  are  nar- 
rowly linked  everywhere,  and  the  same  laws 
govern  the  abundance  of  forms  in  cultivated 
and  in  wild  plants. 

Elementary  species  and  retrograde  varieties 
are  easily  recognizable.  Ever-sporting  varie- 
ties on  the  contrary  are  far  less  obvious,  and 
in  many  cases  their  hereditary  relations  have 

430 


Double  Adaptations  431 

had  to  be  studied  anew.  A  clear  analogy  be- 
tween them  and  corresponding  types  of  wild 
plants  has  yet  to  be  pointed  out.  There  can  be 
no  doubt  that  such  .analogy  exists ;  the  concep- 
tion that  they  should  be  limited  to  cultivated 
plants  is  not  probable.  Striped  flowers  and  va- 
riegated leaves,  changes  of  stamens  into  carpels 
or  into  petals  may  be  extremely  rare  in  the  wild 
state,  but  the  ""  five-leaved  ''  clover  and  a  large 
number  of  monstrosities  cannot  be  said  to  be 
typical  of  the  cultivated  condition.  These,  how- 
ever, are  of  rare  occurrence,  and  do  not  play 
any  important  part  in  the  economy  of  nature. 
In  order  to  attain  a  better  solution  of  the 
problem  we  must  take  a  broader  view  of 
the  facts.  The  wide  range  of  variability  of 
ever-sporting  varieties  is  due  to  the  presence  of 
two  antagonistic  characters  which  cannot  be 
evolved  at  the  same  time  and  in  the  same  or- 
gan, because  they  exclude  on^  another.  AAHien- 
ever  one  is  active,  the  other  must  be  latent.  But 
latency  is  not  absolute  inactivity  and  may  often 
only  operate  to  encumber  the  evolution  of  the 
antagonistic  character,  and  to  produce  large 
numbers  of  lesser  grades  of  its  development. 
The  antagonism  however,  is  not  such  in  the  ex- 
act meaning  of  the  word ;  it  is  rather  a  mutual 
exclusion,  because  one  of  the  opponents  simply 
takes  the  place  of  the  other  when  absent,  or  sup- 


432  Ever-sporting  Varieties 

plements  it  to  the  extent  that  it  may  be  only  im- 
perfectly developed.  This  completion  ordinar- 
ily occurs  in  all  possible  degrees  and  thus 
causes  the  wide  range  of  the  variability.  Nev- 
ertheless it  may  be  wanting,  and  in  the  case  of 
the  double  stocks  only  the  two  extremes  are 
present. 

It  is  rather  difficult  to  get  a  clear  conception 
of  the  substitution,  and  it  seems  necessary  to 
designate  the  peculiar  relationship  between  the 
two  characters  forming  such  a  pair  by  a  simple 
name.  They  might  be  termed  alternating,  if 
only  it  were  clearly  understood  that  the  alterna- 
tion may  be  complete,  or  incomplete  in  all  de- 
grees. Complete  alternation  would  result  in 
the  extremes,  the  incomplete  condition  in  the 
intermediate  states.  In  some  cases  as  with  the 
stocks,  the  first  prevails,  while  in  other  cases,  as 
with  the  poppies,  the  very  extremes  are  only 
rarely  met  with. 

Taking  such  an  alternation  as  a  real  char- 
acter of  the  ever-sporting  varieties,  a  wide 
range  of  analogous  cases  is  at  once  revealed 
among  the  normal  qualities  of  wild  plants.  Al- 
ternation is  here  almost  universal.  It  is  the  ca- 
pacity of  young  organs  to  develop  in  two  diverg- 
ing directions.  The  definitive  choice  must  be 
made  in  extreme  youth,  or  often  at  a  relatively 
late  period  of  development.     Once  made,  this 


Double  Adaptations  433 

choice  is  final,  and  a  further  change  does  not  oc- 
cur in  the  normal  course  of  things. 

The  most  curious  and  most  suggestive  in- 
stance of  such  an  alternation  is  the  case  of  the 
water-persicaria  or  Polygonum  amphibium.  It 
is  known  to  occur  in  two  forms,  one  aquatic  and 
the  other  terrestrial.  These  are  recorded  in 
systematic  works  as  varieties,  and  are  described 
under  the  names  of  P.  amphibium  var.  natans 
Moench,  and  P.  amphibium  var.  terrestre  Leers 
or  P,  amphibium  var.  terrestris  Moench.  Such 
authorities  as  Koch  in  his  German  flora,  and 
Grenier  and  Godron  in  their  French  flora  agree 
in  the  conception  of  the  two  forms  as  varieties. 

Notwithstanding  this,  the  two  varieties  may 
often  be  observed  to  sport  into  one  another. 
They  are  only  branches  of  the  same  plant, 
grown  under  different  conditions.  The  aquatic 
form  has  floating  or  submerged  stems  with  ob- 
long or  elliptic  leaves,  which  are  glabrous  and 
have  long  petioles.  The  terrestrial  plants  are 
erect,  nearly  simple,  more  or  less  hispid 
throughout,  with  lanceolate  leaves  and  short  pe- 
tioles, often  nearly  sessile.  The  aquatic  form 
flowers  regularly,  producing  its  peduncle  at 
right  angles  from  the  floating  stems,  but  the 
terrestrial  specimens  are  ordinarily  seen  with- 
out flower-spikes,  which  are  but  rarely  met  with, 
at  least  as  far  as  my  own  experience  goes.     In- 


434  Ever-sporting  Varieties 

termediate  forms  are  very  rare,  perhaps  wholly 
wanting,  though  in  swamps  the  terrestrial 
plants  may  often  vary  widely  in  the  direction  of 
the  floating  type. 

That  both  types  sport  into  each  other  has 
long  been  recognized  in  field-observations,  and 
has  been  the  ground  for  the  specific  name  of 
amphibium,  though  in  this  respect  herbarium- 
material  seems  usually  to  be  scant.  The  mat- 
ter has  recently  been  subjected  to  critical  and 
experimental  studies  by  the  Belgian  botanist 
Massart,  who  has  shown  that  by  transplanting 
the  forms  into  the  alternate  conditions,  the 
change  may  always  be  brought  about  arti- 
ficially. If  floating  plants  are  established  on 
the  shore  they  make  ascending  hairy  stems,  and 
if  the  terrestrial  shoots  are  submerged,  their 
buds  grow  into  long  and  slack,  aquatic  stems. 
Even  in  such  experiments,  intermediates  are 
rare,  both  types  agreeing  completely  with  the 
corresponding  models  in  the  wild  state. 

Among  all  the  previously  described  cases  of 
horticultural  plants  and  monstrosities  there  is 
no  clearer  case  of  an  ever-sporting  variety  than 
this  one  of  the  water-persicaria.  The  var. 
terrestris  sports  into  the  var.  natans,  and 
as  often  as  the  changing  life  conditions  may 
require  it.  It  is  true  that  ordinary  sports  oc- 
cur without  our  discerning  the  cause  and  with- 


Double  Adaptations  435 

out  any  relation  to  adaptation.  This  however 
is  partly  due  to  our  lack  of  knowledge, 
and  partly  to  the  general  rule  that  in  nature 
only  such  sports  as  are  useful  are  spared  by 
natural  selection,  and  what  is  useful  we  ordi- 
narily term  adaptive. 

Another  side  of  the  question  remains  to  be 
considered.  The  word  variety,  as  is  now  be- 
coming generally  recognized,  has  no  special 
meaning  whatever.  But  here  it  is  assumed  in 
the  clearly  defined  sense  of  a  systematic  va- 
riety, which  includes  all  subdivisions  of  spe- 
cies. Such  subdivisions  may  be,  from  a 
biological  point  of  view,  elementary  species  and 
also  be  eversporting  varieties.  They  may  be 
retrograde  varieties,  and  the  two  alternating 
types  may  be  described  as  separate  varieties. 

It  is  readily  granted  that  many  writers 
would  not  willingly  accept  this  conclusion.  But 
it  is  simply  impossible  to  avoid  it.  The  two 
forms  of  the  water-persicaria  must  remain 
varieties,  though  they  are  only  types  of  the  dif- 
ferent branches  of  a  single  plant. 

If  not,  hundreds  and  perhaps  thousands  of 
analogous  cases  are  at  once  exposed  to  doubt, 
and  the  whole  conception  of  systematic  varie- 
ties would  have  to  be  thrown  over.  Biologists 
of  course  would  have  no  objection  to  this,  but 
the  student  of  the  flora  of  any  given  country 


436  Ever-sporting  Varieties 

or  region  requires  the  systematic  subdivisions 
and  should  always  use  his  utmost  efforts  to 
keep  them  as  they  are.  There  is  no  intrinsic 
difficulty  in  the  statement  that  different  parts  of 
the  same  plant  should  constitute  different  va- 
rieties. 

In  some  cases  different  branches  of  the  same 
plant  have  been  described  as  species.  So  for 
instance  with  the  climbing  forms  of  figs.  Un- 
der the  name  of  Ficus  repens  a  fine  little  plant  is 
quite  commonly  cultivated  as  a  climber  in  flower 
baskets.  It  is  never  seen  bearing  figs.  On  the 
other  hand  a  shrub  of  our  hothouses  called 
Ficus  stipulata,  is  cultivated  in  pots  and  makes 
a  small  tree  which  produces  quite  large,  though 
non-edible  figs.  Now  these  two  species  are  sim- 
ply branches  of  the  same  plant.  If  the  repens  is 
allowed  to  climb  up  high  along  the  walls  of  the 
hothouses,  it  will  at  last  produce  stipulata- 
branches  with  the  corresponding  fruits.  Ficus 
radicans  is  another  climbing  form,  correspond- 
ing to  the  shrub  Ficus  ulmifolia  of  our  glass- 
houses. And  quite  the  same  thing  occurs  with 
ivy,  the  climbing  stems  of  which  never  flower, 
but  always  first  produce  erect  and  free  branches 
with  rhombic  leaves.  These  branches  have 
often  been  used  as  cuttings  and  yield  little  erect 
and  richly  flowering  shrubs,  which  are  known  in 


Double  Adaptations  437 

horticulture  under  tlie  varietal  name  of  Uede- 
ra  Helix  arborea. 

Manifestly  this  classification  is  as  nearly 
right  as  that  of  the  two  varieties  of  the  water- 
persicaria.  Going  one  step  further,  we  meet 
with  the  very  interesting  case  of  alpine  plants. 
The  vegetation  of  the  higher  regions  of  moun- 
tains is  commonly  called  alpine,  and  the  plants 
show  a  large  number  of  common  features,  dif- 
ferentiating them  from  the  flora  of  lower  sta- 
tions. The  mountain  plants  have  small  and 
dense  foliage,  with  large  and  brightly-colored 
flowers.  The  corresponding  forms  of  the  low- 
lands have  longer  and  weaker  stems,  bearing 
their  leaves  at  greater  distances,  the  leaves 
themselves  being  more  numerous.  The  alpine 
forms,  if  perennial,  have  thick,  strongly  de- 
veloped and  densely  branched  rootstocks  with 
heavy  roots,  in  which  a  large  amount  of  food- 
material  is  stored  up  during  the  short  summer, 
and  is  available  during  the  long  winter  months 
of  the  year. 

Some  species  are  peculiar  to  such  high  al- 
titudes, while  many  forms  from  the  lowlands 
have  no  corresponding  type  on  the  mountains. 
But  a  large  number  of  species  are  common  to 
both  regions,  and  here  the  difference  of  course  is 
most  striking.  Lotus  cornicidatus  and  Cala- 
mintJia  Acinos,  Calluna  vidgaris  and  Campa- 


438  Ever-sporting  Varieties 

7iula  rotundifolia  may  be  quoted  as  instances, 
and  every  botanist  who  bas  visited  alpine  re- 
gions may  add  other  examples.  Even  the  edel- 
weiss of  the  Swiss  Alps,  Gnaphalium  Leonto- 
podium,  loses  its  alpine  characters,  if  cultivated 
in  lowland  gardens.  Between  such  lowland  and 
alpine  forms  intermediates  regularly  occur. 
They  may  be  met  with  whenever  the  range  of  the 
species  extends  from  the  plains  upward  to  the 
limit  of  eternal  snow. 

In  this  case  the  systematists  formerly  enu- 
merated the  alpine  plants  as  forma  alpestris,  but 
whenever  the  intermediate  is  lacking  the  term 
varietas  alpestris  was  often  made  use  of. 

It  is  simply  imjoossible  to  decide  concerning 
the  real  relation  between  the  alpine  and  low- 
land  types  without  experiments.  About  the 
middle  of  the  last  century  it  was  quite  a  com- 
mon thing  to  collect  plants  not  only  for  her- 
barium-material, but  also  for  the  purpose  of 
planting  them  in  gardens  and  thus  to  observe 
their  behavior  under  new  conditions.  This 
was  done  with  the  acknowledged  purpose 
of  investigating  the  systematic  significance  of 
observed  divergencies.  Whenever  these  held 
good  in  the  garden  they  were  considered  to  be 
reliable,  but  if  they  disappeared  they  were  re- 
garded as  the  results  of  climatic  conditions, 
or  of  the  influence  of  soil  or  nourishment.     Be- 


Double  Adaptations  431) 

tween  these  two  alternatives,  many  writers 
have  tried  to  decide,  by  transplanting  their 
specimens  after  some  time  in  the  garden,  into 
arid  or  sandy  soil,  in  order  to  see  whether  they 
would  resume  their  alpine  character. 

Among  the  systematists  who  tested  plants  in 
this  way,  Nageli  especially,  directed  his  atten- 
tion to  the  hawkweeds  or  Hieracium.  On 
the  Swiss  Alps  they  are  very  small  and  ex- 
hibit all  the  characters  of  the  pure  alpine  type. 
Thousands  of  single  plants  were  cultivated  by 
him  in  the  botanical  garden  of  Munich,  partly 
from  seed  and  partly  from  introduced  root- 
stocks.  Here  they  at  once  assumed  the 
tall  stature  of  lowland  forms.  The  identical 
individual,  which  formerly  bore  small  rosettes 
of  basal  leaves,  with  short  and  unbranched 
flower-stalks,  became  richly  leaved  and  often 
produced  quite  a  profusion  of  flower-heads  on 
branched  stems.  If  then  they  were  trans- 
planted to  arid  sand,  though  remaining  in  the 
same  garden  and  also  under  the  same  climatic 
conditions  they  resumed  their  alpine  charac- 
ters. This  proved  nutrition  to  be  the  cause 
of  the  change  and  not  the  climate. 

The  latest  and  most  exact  researches  on  this 
subject  are  due  to  Bonnier,  who  has  gone  into 
all  the  details  of  the  morphologic  as  well  as 
of     the     physiologic     side     of     the     problem. 


440  Ever-sporting  Varieties 

His  purpose  was  the  study  of  partial  variabil- 
ity under  the  influence  of  climate  and  soil.  In 
every  experiment  he  started  from  a  single  indi- 
vidual, divided  it  into  two  parts  and  planted 
one  half  on  a  mountain  and  the  other  half  on 
the  plain.  The  garden  cultures  were  made 
chiefly  at  Paris  and  Fontainebleau,  the  alpine 
cultures  partly  in  the  Alps,  partly  in  the  Py- 
renees. From  time  to  time  the  halved  plants 
were  compared  with  each  other,  and  the  cul- 
tures lasted,  as  a  rule,  during  the  lifetime  of  the 
individual,  often  covering  many  years. 

The  common  European  frostweed  or  Helian- 
themum  vulgare  will  serve  to  illustrate  his  re- 
sults. A  large  plant  growing  in  the  Pyrenees  in 
an  altitude  of  2400  meters  was  divided.  One  half 
was  replanted  on  the  same  spot,  and  the  other 
near  Cadeac,  at  the  base  of  the  mountain  range 
(740  M.).  In  order  to  exclude  the  etfect  of  a 
change  of  soil,  a  quantity  of  the  earth  from  the 
original  locality  was  brought  into  the  garden 
and  the  plant  put  therein.  Further  control- 
experiments  were  made  at  Paris.  As  soon  as 
the  two  halved  individuals  commenced  to  grow 
and  produced  new  shoots,  the  influence  of  tlie 
ditferent  climates  made  itself  felt.  On  the 
mountain,  the  underground  portions  remained 
strong  and  dense,  the  leaves  and  internodes 
small  and  hairy,   the  flowering  stems  nearly 


Double  Adaptations  441 

procumbent,  the  flowers  being  large  and  of  a 
deep  yellow.  At  Cadeac  and  at  Paris  the  whole 
plant  changed  at  once,  the  shoots  becoming 
elongated  and  loose,  with  broad  and  flattened, 
rather  smooth  leaves  and  numerous  pale-hued 
flowers.  The  anatomical  structure  exhibited  cor- 
responding differences,  the  intercellular  spaces 
being  small  in  the  alpine  plant  and  large  in  the 
one  grown  in  the  lowlands,  the  wood-tissues 
strong  in  the  first  and  weak  in  the  second  case. 

The  milfoil  {Achillea  Millefolium)  served 
as  a  second  example,  and  the  experiments  were 
carried  on  in  the  same  localities.  The  long  and 
thick  rootstocks  of  the  alpine  plant  bearing 
short  stems  only  with  a  few  dense  corymbs 
contrasted  markedly  with  the  slender  stems, 
loose  foliage  and  rich  groups  of  flowerheads  of 
the  lowland  plant.  The  same  differences  in  in- 
ner and  outer  structures  were  observed  in  nu- 
merous instances,  showing  that  the  alpine  type 
in  these  cases  is  dependent  on  the  climate,  and 
that  the  capacity  for  assuming  the  antagonistic 
characters  is  present  in  every  individual  of  the 
species.  The  external  conditions  decide  which 
of  them  becomes  active  and  which  remains  in- 
active, and  the  case  seems  to  be  exactly  paral- 
lel to  that  of  the  water-persicaria. 

In  the  experiments  of  Bonnier  the  influence 
of  the  soil  was,  as  a  rule,  excluded  by  trans- 


442  Ever-sporting  Varieties 

planting  part  of  the  original  earth  with  tlie 
transplanted  half  of  the  plant.  From  this  he 
concluded  that  the  observed  changes  were  due 
to  the  inequality  of  the  climate.  This  involved 
three  main  factors,  light,  moisture  and  tem- 
perature. On  the  mountains  the  light  is  more 
intense,  the  air  drier  and  cooler.  Control-ex- 
periments were  made  on  the  mountains,  de- 
priving the  plants  of  part  of  the  light.  In  va- 
rious ways  they  were  more  or  less  shaded,  and 
as  a  rule  responded  to  this  treatment  in  the 
same  way  as  to  transplantation  to  the  plain 
below.  Bonnier  concluded  that,  though  more 
than  one  factor  takes  part  in  inciting  the 
morphologic  changes,  light  is  to  be  consid- 
ered as  the  chief  agency.  The  response  is  to 
be  considered  as  a  useful  one,  as  the  whole 
structure  of  the  alpine  varieties  is  fitted  to  pro- 
duce a  large  amount  of  organic  material  in  a 
short  time,  which  enables  the  plants  to  thrive 
during  the  short  summers  and  long  winters  of 
their  elevated  stations. 

In  connection  with  these  studies  on  the  in- 
fluences of  alpine  climates.  Bonnier  has  inves- 
tigated the  internal  structure  of  arctic  plants, 
and  made  a  series  of  experiments  on  growth 
in  continuous  electric  light.  The  arctic  climate 
is  cold,  but  wet,  and  the  structure  of  the  leaves 
is  correspondingly  loose,  though  the  plants  be- 


Double  Adaptations  443 

come  as  small  as  on  the  Alps.  Continuous  elec- 
tric light  had  very  curious  effects;  the  plants 
became  etiolated,  as  if  growing  in  darkness, 
with  the  exception  that  they  assumed  a  deep 
green  tinge.  They  showed  more  analogy  with 
the  arctic  than  with  the  alpine  type. 

The  influence  of  the  soil  often  produces 
changes  similar  to  that  of  climate.  This  was 
shown  by  the  above  cited  experiments  of  Na- 
geli  with  the  hawkweeds,  and  may  easily  be 
controlled  in  other  cases.  The  ground-honey- 
•suckle  or  Lotus  corniculatus  grows  in  Holland 
partly  on  the  dry  and  sandy  soil  of  the  dunes, 
and  occasionally  in  meadows.  It  is  small  and 
dense  in  the  first  case,  with  orange  and  often 
very  darkly  colored  petals,  while  it  is  loose  and 
green  in  the  meadows,  with  yellower  flowers. 
Numerous  analogous  cases  might  be  given.  On 
mountain  slopes  in  South  Africa,  and  especial- 
ly in  Natal,  a  species  of  composite  is  found, 
which  has  been  introduced  into  culture  and  is 
used  as  a  hanging  plant.  It  is  called  Othonna 
crassifolia  and  has  fleshy,  nearly  cylindrical 
leaves,  and  exactlv  mimics  some  of  the  crassu- 
laceous  species.  On  dry  soil  the  leaves  become 
shorter  and  thicker  and  assume  a  reddisli 
tinge,  the  stems  remain  short  and  woody  and 
bear  their  leaves  in  dense  rosettes.  On  moist 
and     rich     garden-soil     this    aspect     becomes 


444  Ever-sporting  Varieties 

changed  at  once,  the  stems  grow  longer  and 
of  a  deeper  green.  Intermediates  occur,  but 
notwithstanding  this  the  two  extremes  consti- 
tute clearly  antagonistic  types. 

The  flora  of  the  deserts  is  known  to  exhibit 
a  similar  divergent  type.  Or  rather  two  types, 
'one  adapted  to  paucity  of  water,  and  the  other 
to  a  storage  of  fluid  at  one  season  in  order  to 
make  use  of  it  at  other  times,  as  is  the  case  with 
the  cactuses.  Limiting  ourselves  to  the  alter- 
nate group,  we  observe  a  rich  and  dense  branch- 
ing, small  and  compact  leaves  and  extraordi- 
narily long  roots.  Here  the  analogy  with  the 
alpine  varieties  is  manifest,  and  the  dryness 
of  the  soil  evidently  affects  the  plants  in  a  sim- 
ilar way,  as  do  the  conditions  of  life  in  alpine 
regions.  The  question  at  once  comes  up  as  to 
whether  here  too  we  have  only  instances  of 
partial  variability,  and  whether  many  of  the 
typical  desert-species  would  lose  their  pecu- 
liar character  by  cultivation  under  ordinary 
conditions.  The  varieties  of  Monardella  ma- 
crantha,  described  by  Hall,  from  the  San  Ja- 
cinto Mountain,  Cal.,  are  suggestive  of  such 
an  intimate  analogy  with  the  cases  studied  by 
Bonnier,  that  it  seems  probable  that  they  might 
yield  similar  results,  if  tested  by  the  same 
method. 

Leaving  now  the  description  of  these  special 


Double  Adaptations  445 

cases,  we  may  resume  our  theoretical  discus- 
sion of  the  subject,  and  try  to  get  a  clearer  in- 
sight into  the  analogy  of  ever-sporting  varie- 
ties and  the  wild  species  quoted.  All  of  them 
may  be  characterized  by  the  general  term  of 
dimorphism.  Two  types  are  always  present, 
though  not  in  the  same  individual  or  in  the  same 
organ.  They  exclude  one  another,  and  dur- 
ing their  juvenile  stage  a  decision  is  taken  in 
one  direction  or  in  the  other.  Now,  according 
to  the  theory  of  natural  selection,  wild  species 
can  only  retain  useful  or  at  least  innocuous 
qualities,  since  all  mutations  in  a  wrong  direc- 
tion must  perish  sooner  or  later.  Cultivated 
species  on  the  other  hand  are  known  to  be 
largely  endowed  with  qualities,  which  would 
be  detrimental  in  the  wild  condition.  Mon- 
strosities are  equally  injurious  and  could  not 
hold  their  own  if  left  to  themselves. 

These  same  principles  may  be  applied  to 
ever-sporting  or  antagonistic  pairs  of  charac- 
ters. According  to  the  theory  of  mutations 
such  pairs  may  be  either  useful  or  useless.  But 
only  the  useful  will  stand  further  test,  and  if 
they  find  suitable  conditions  will  become  spe- 
cific or  varietal  characters.  On  this  conclusion 
it  becomes  at  once  clear,  why  natural  di- 
morphism is,  as  a  rule,  a  very  useful  quality, 
while     the     cultivated     dimorphous    varieties 


446  Ever-sporting  Varieties 

strike  us  as  something  unnatural.  The  rela- 
tion between  cause  and  effect,  is  in  truth  other 
than  it  might  seem  to  be  at  first  view,  but  nev- 
ertheless it  exists,  and  is  of  the  highest  impor- 
tance. 

From  this  same  conclusion  we  may  further 
deduce  some  explanation  of  the  hereditary 
races  characterized  bv  monstrosities.  It  is 
quite  evident  that  the  twisted  teasels  are  in- 
adequate for  the  struggle  with  their  tall  con- 
geners, or  with  the  surrounding  plants.  Hence 
the  conclusion  that  a  pure  and  exclusively 
twisted  race  would  soon  die  out.  The  fact  that 
such  races  are  not  in  existence  finds  its  expla- 
nation in  this  circumstance,  and  therefore  it 
does  not  prove  the  impossibility  or  even  the  im- 
probability that  some  time  a  pure  twisted  race 
might  arise.  If  chance  should  put  such  an  ac- 
cidental race  in  the  hands  of  an  experimenter, 
it  could  be  protected  and  preserved,  and  hav- 
ing no  straight  atavistic  branches,  but  being 
twisted  in  all  its  organs,  might  yield  the  most 
curious  conceivable  monstrosity,  surpassing 
even  the  celebrated  dwarf  twisted  shrubs  of 
Japanese  horticulturists. 

Such  varieties  however,  do  not  exist  at  pres- 
ent. The  ordinary  twisted  races  on  the  other 
hand,  are  found  in  the  wild  state  and  have  only 
to  be  isolated  and  cultivated  to  yield  large  num- 


Double  Adaptations  447 

bers  of  twisted  individuals.  In  nature  they  are 
able  to  maintain  themselves  during  long  cen- 
turies, quite  as  well  as  normal  species  and  va- 
rieties. But  they  owe  this  quality  entirely  to 
their  dimorphous  character.  A  twisted  race  of 
teasels  might  consist  of  successive  generations 
of  tall  atavistic  individuals,  and  produce  year- 
ly some  twisted  specimens,  which  might  be  de- 
stroyed every  time  before  ripening  their  seeds. 
Reasoning  from  the  evidence  available,  and 
from  analogous  cases,  the  variety  would,  even 
under  such  extreme  circumstances,  be  able  to 
last  as  long  as  any  other  good  variety  or  ele- 
mentary species.  And  it  seems  to  me  that  this 
explanation  makes  clear  how  it  is  possible  that 
varieties,  which  are  potentially  rich  in  their  pe- 
culiar monstrosity,  are  discovered  from  time  to 
time  among  plants  when  tested  by  experimental 
methods. 

Granting  these  conclusions,  monstrosities  on 
the  one  side,  and  dimorphous  wild  species  on 
the  other,  constitute  the  most  striking  examples 
of  the  inheritance  of  latent  characters. 

The  bearing  of  the  phenomena  of  dimorphism 
upon  the  principles  of  evolution  formulated  by 
Lamarck,  and  modified  by  his  followers  to  con- 
stitute Neo-Lamarckianism,  remains  to  be  con- 
sidered. Lamarck  assumed  that  the  external 
conditions  directly  affected  the  organisms  in 


448  Ever-sporting  Varieties 

such  a  way  as  to  make  them  better  adapted  to 
life,  under  prevailing  circumstances.  Nageli 
gave  to  this  conception  the  name  ""  Theory 
of  direct  causation  "  (Theorie  der  direc- 
ten  Bewirkung),  and  it  has  received  the  ap- 
proval of  Von  Wettstein,  Strasburger  and  other 
German  investigators.  According  to  this  con- 
ception a  plant,  when  migrating  from  lowlands 
into  the  mountains  would  slowly  be  changed 
and  gradually  assume  alpine  habits.  Once  ac- 
quired this  habit  would  become  fixed  and  attain 
the  rank  of  specific  characters.  In  testing  this 
theory  by  field-observations  and  culture-exper- 
iments, the  defenders  of  the  Nagelian  principle 
could  easily  produce  evidence  upon  the  first 
point.  The  change  of  lowland-plants  into  al- 
pine varieties  can  be  brought  about  in  numer- 
ous cases,  and  corresponding  changes  under 
the  influence  of  soil,  or  climate,  or  life-condi- 
tions are  on  record  for  the  most  various  charac- 
ters and  qualities. 

The  second  point,  however,  is  as  difficult  to 
prove  as  the  first  is  of  easy  treatment.  If  after 
hundreds  and  thousands  of  years  of  exposure  to 
alpine  or  other  extreme  conditions  a  fixed 
change  is  proved  to  have  taken  place,  the  ques- 
tion remains  unanswered,  whether  the  change 
has  been  a  gradual  or  a  sudden  one.  Darwin 
pointed  out  that  long  periods  of  life  afford  a 


Double  Adaptations  449 

chance  for  a  sudden  change  in  the  desired  di- 
rection, as  well  as  for  the  slow  accumulation  of 
slight  deviations.  Any  mutations  in  a  wrong 
direction  would  at  once  be  destroyed,  but  an 
accidental  change  in  a  useful  way  would  be 
preserved,  and  multiply  itself.  If  in  the  course 
of  centuries  this  occurred,  they  woukl  be  near- 
ly sure  to  become  established,  however  rare  at 
the  outset.  Hence  the  positive  assertion  is 
scarcely  capable  of  direct  proof. 

On'  the  other  hand  the  negative  assertion 
must  be  granted  full  significance.  If  the  al- 
pine climate  has  done  no  more  than  produce  a 
transitory  change,  it  is  clear  that  thousands 
of  years  do  not,  necessarily,  cause  constant 
and  specific  alterations.  This  requirement  is 
one  of  the  indispensable  supports  of  the  La- 
marckian  theory.  The  matter  is  capable  of 
disproof  however,  and  such  disproof  seems  to 
be  afforded  by  the  direct  evidence  of  the  pres- 
ent condition  of  the  alpine  varieties  at  large, 
and  by  many  other  similar  cases. 

Among  these  the  observations  of  Holter- 
mann  on  some  desert-plants  of  Ceylon  are  of 
the  highest  value.  Moreover  they  touch  ques- 
tions which  are  of  wide  importance  for  the 
study  of  the  biology  of  American  deserts.  For 
this  reason  I  mav  be  allowed  to  introduce  them 

ft'' 

here  at  some  length. 


450  Ever-sporting  Varieties 

The  desert  of  Kaits,  in  Northern  Ceylon, 
nourishes  on  its  dry  and  torrid  sands  some 
species,  represented  by  a  large  number  of  in- 
dividuals, together  with  some  rarer  plants. 
The  commonest  forms  are  Erigeron  asteroides, 
Vernonia  cinerea^  Laurea  pinnatifida,  Vicoa  au- 
riculata^  Heylandia  latehrosa  and  Chrysopo- 
gon  montanus.  In  direct  contrast  with  the  or- 
dinary desert-types  they  have  a  thin  epidermis, 
with  exposed  stomata,  features  that  ordinarily 
were  characteristic  of  species  of  moister  re- 
gions. They  are  annuals,  growing  rapidly, 
blooming  and  ripening  their  seeds  before  the 
height  of  the  dry  season.  Evidently  they  are 
to  be  considered  as  the  remainder  of  the  flora 
of  a  previous  period,  when  the  soil  had  not  yet 
become  arid.  They  might  be  called  relics.  Of 
course  they  are  small  and  dwarf-like,  when  com- 
pared with  allied  forms. 

These  curious  little  desert-plants  disprove 
the  Nagelian  views  in  two  important  points. 
First,  they  show  that  extreme  conditions  do  not 
necessarily  change  the  organisms  subjected  to 
them,  in  a  desirable  direction.  During  the 
many  centuries  that  these  plants  must  have  ex- 
isted in  the  desert  in  annual  generations,  no 
single  feature  in  the  anatomical  structure  has 
become  changed.  Hence  the  conclusion  that 
small  leaves,   abundant   rootstocks   and   short 


Double  Adaptations  451 

stems,  a  dense  foliage,  a  strongly  cuticularized 
epidermis,  few  and  narrow  air-cavities  in  the 
tissues  and  all  the  long  range  of  characteris- 
tics of  typical  desert-plants  are  not  a  simple 
result  of  the  influence  of  climate  and  soil. 
There  is  no  direct  influence  in  this  sense. 

The  second  point,  in  Avhich  Nageli's  idea  is 
broken  down  by  Holtermann's  observations,  re- 
sults from  the  behavior  of  the  plants  of  the 
Kaits  desert  when  grown  or  sown  on  garden- 
soil.  When  treated  in  this  way  they  at  once 
lose  the  only  peculiarity  which  might  be  con- 
sidered as  a  consequence  of  the  desert-life  of 
their  ancestors,  their  dwarf  stature.  They  be- 
have exactly  like  the  alpine  plants  in  Bonnier's 
experiments,  and  with  even  more  striking  dif- 
ferences. In  the  desert  they  attain  a  height 
of  a  few  centimeters,  but  in  the  garden  they 
attain  half  a  meter  and  more  in  height.  Noth- 
ing in  the  way  of  stability  has  resulted  from  the 
action  of  the  dry  soil,  not  even  in  such  a  minor 
point  as  the  height  of  the  stems. 

From  these  facts  and  discussions  we  may 
conclude  that  double  adaptation  is  not  induced 
by  external  influences,  at  least  not  in  any  way 
in  which  it  might  be  of  use  to  the  plant.  Tt 
may  arise  by  some  unknown  cause,  or  may 
not  be  incited  at  all.  In  the  first  case  the  plant 
becomes  capable  of  living  under  the  altemat- 


452  Ever-sporting  Varieties 

ing  circumstances,  and  if  growing  near  the 
limits  of  such  regions  it  will  overlap  and  get 
into  the  new  area.  All  other  species,  which  did 
not  acquire  the  double  habit,  are  of  course  ex- 
cluded, with  such  curious  exceptions  as  those 
of  Kaits.  The  typical  vegetation  under  such 
extreme  conditions  however,  finds  explanation 
quite  as  well  by  the  one  as  by  the  other  view. 

Leaving  these  obvious  cases  of  double  adap- 
tation, there  still  remains  one  point  to  be  con- 
sidered. It  is  the  dwarf  stature  of  so  many 
desert  and  alpine  plants.  Are  these  dwarfs 
only  the  extremes  of  the  normal  fluctuating  va- 
riability, or  is  their  stature  to  be  regarded  as 
the  expression  of  some  peculiar  adaptive  but 
latent  quality?  It  is  as  yet  difficult  to  decide 
this  question,  because  statistical  studies  of  this 
form  of  variability  are  still  wanting.  The  ca- 
pacity of  ripening  the  seed  on  individuals  of 
dwarf  stature  however,  is  not  at  all  a  uni- 
versal accompaniment  of  a  variable  height. 
Hence  it  cannot  be  considered  as  a  necessary 
consequence  of  it.  On  the  other  hand  the  dwarf 
varieties  of  numerous  garden-plants,  as  for  in- 
stance: of  larkspurs,  snapdragon,  opium-pop- 
pies and  others  are  quite  stable  and  thence  are 
obviously  due  to  peculiar  characteristics.  Such 
characteristics,  if  combined  with  tall  stature 
into  a  pair  of  antagonists,  would  yield  a  double 


Double  Adaptations  453 

adaptation,  and  on  such  a  base  a  hypothetical 
explanation  could  no  doubt  be  rested. 

Instead  of  discussing  this  problem  from  the 
theoretical  side,  I  prefer  to  compare  those  spe- 
cies which  are  capable  of  assuming  a  dwarf 
stature  under  less  uncommon  conditions  than 
those  of  alpine  and  desert-plants.  Many  weeds 
of  our  gardens  and  many  wild  species  have  this 
capacity.  They  become  very  tall,  with  large 
leaves,  richly  branched  stems  and  numerous 
flowers  in  moist  and  rich  soil.  On  bad  soil,  or 
if  germinating  too  late,  when  the  season  is 
drier,  they  remain  very  small,  producing  only 
a  few  leaves  and  often  limiting  themselves  to 
one  flower-head.  This  is  often  seen  with  thorn- 
apples  and  amaranths,  and  even  with  oats  and 
rye,  and  is  notoriously  the  case  with  buck- 
wheat. G-auchery  has  observed  that  the  ex- 
tremes differ  often  as  much  from  one  another 
as  1 :10.  In  the  case  of  the  Canadian  horse- 
weed  or  Erigeron  canadensis,  which  is  widely 
naturalized  in  Europe,  the  tallest  specimens 
are  often  twenty-five  times  as  tall  as  the  small- 
est, the  difference  increasing  to  greater  ex- 
tremes, if  besides  the  main  stem,  the  length  of 
the  numerous  branches  of  the  tall  plants  are 
taken  into  consideration.  Other  instances 
studied  by  the  French  investigator  are  Ery- 
thraea  pulchella  and  Calamintha  Acinos. 


454  Ever-sporthig  Varieties 

Dimorphism  is  of  universal  occurrence  in  the 
whole  vegetable  kingdom.  In  some  cases  it  is 
typical,  and  may  easily  be  discerned  from  ex- 
treme flutuating  variability.  In  others  the  con- 
trast is  not  at  all  obvious,  and  a  closer 
investigation  is  needed  to  decide  between  the 
two  possibilities.  Sometimes  the  adaptive  qual- 
ity is  evident,  in  other  cases  it  is  not.  A  large 
number  of  plants  bear  two  kinds  of  leaves  linked 
with  one  another  by  intermediate  forms.  Often 
the  first  leaves  of  a  shoot,  or  those  of  accident- 
ally strong  shoots,  exhibit  deviating  shapes, 
and  the  usefulness  of  such  occurrences  seems  to 
be  quite  doubtful.  The  elongation  of  stems  and 
linear  leaves,  and  the  reduction  of  lateral  or- 
gans in  darkness,  is  manifestly  an  adaptation. 
Many  plants  have  stolons  with  double  adapta- 
tions which  enable  them  to  retain  their  char- 
acter of  underground  stems  with  bracts  or  to 
exchange  it  for  the  characteristics  of  erect 
stems  with  green  leaves  according  to  the  outer 
circumstances.  In  some  shrubs  and  trees  the 
capacity  of  a  number  of  buds  to  produce  either 
flowers  or  shoots  with  leaves  seems  to  be  in 
the  same  condition.  The  capacity  of  producing 
spines  is  also  a  double  adaptation,  active  on 
dry  and  arid  soil  and  latent  in  a  moist  climate 
or  under  cultivation,  as  with  the  wild  and  cul- 
tivated apple,  and  in  the  experiments  of  Lo- 


Double  Adaptations  455 

tlielier  with  Berheris,  Lycium  and  other  species, 
which  lose  their  spines  in  damp  air. 

In  some  conifers  the  evolution  of  horizontal 
branches  may  be  modified  by  simply  turning 
the  buds  upside  down.  Or  the  lateral  branches 
can  be  induced  to  become  erect  stems  by 
cutting  off  the  normal  summit  of  a  tree.  Nu- 
merous organs  and  functions  lie  dormant  un- 
til aroused  by  external  agencies,  and  many 
other  cases  could  be  cited,  showing  the  wide 
occurrence  of  double  adaptation. 

There  are,  however,  two  points,  which  should 
not  be  passed  over  without  some  mention.  One 
of  them  is  the  influence  of  sun  and  shade  on 
leaves,  and  the  other  the  atavistic  forms,  often 
exhibited  during  the  juvenile  period. 

The  leaves  of  many  plants,  and  especially 
those  of  some  shrubs  and  trees,  have  the  ca- 
pacity of  adapting  themselves  either  to  intense 
or  to  diffuse  light.  On  the  circumference  of  the 
crown  of  a  tree  the  light  is  stronger  and  the 
leaves  are  small  and  thick,  with  a  dense  tissue. 
In  the  inner  parts  of  the  crown  the  light  is 
weak  and  the  leaves  are  broader  in  order  to 
get  as  much  of  it  as  possible.  They  become 
larger  but  thinner,  consisting  often  of  a  small 
number  of  cell  layers.  The  definitive  forma- 
tion is  made  in  extreme  youth,  often  even 
during  the  previous  summer,  at  the  time  of  the 


456  Ever-sporting  Varieties 

very  first  evolution  of  the  young  organs  within 
the  buds.  Iris,  and  Lactuca  Scariola  or  the 
prickly  lettuce,  and  many  other  plants  afford 
similar  instances.  As  the  definitive  decision 
must  be  made  in  these  cases  long  before  the  di- 
rect influence  of  the  conditions  which  would 
make  the  change  useful  is  felt,  it  is  hardly  con- 
ceivable how  they  could  be  ascribed  to  this 
cause. 

It  is  universally  known  that  many  plants 
show  deviating  features  when  very  young,  and 
that  these  often  remind  us  of  the  characters  of 
their  probable  ancestors.  Many  plants  that 
must  have  been  derived  from  their  nearest  sys- 
tematic relatives,  chiefly  by  reductions,  are 
constantly  betraying  this  relation  by  a  repeti- 
tion of  the  ancestral  marks  during  their 
youth. 

There  can  be  hardly  a  doubt  that  the  general 
law  of  natural  selection  prevails  in  such  cases 
as  it  does  in  others.  Or  stated  otherwise,  it  is 
very  probable,  that  in  most  cases  the  atavistic 
characters  have  been  retained  during  youth 
because  of  their  temporary  usefulness.  Un- 
fortunately, our  knowledge  of  utility  of  quali- 
ties is  as  yet  very  incomplete.  Here  we  must 
assume  that  what  is  ordinarily  spared  by  nat- 
ural selection  is  to  be  considered  as  useful, 


Double  Adaptations  457 

until  direct  experimental  investigations  have 
been  made. 

So  it  is  for  instance  with  the  submerged  leaves 
of  water-plants.  As  a  rule  they  are  linear,  or 
if  compound,  are  reduced  to  densely  branching 
filiform  threads.  Hence  we  may  conclude  that 
this  structure  is  of  some  use  to  them.  Now 
two  European  and  some  corresponding  Amer- 
ican species  of  water-parsnip,  the  Slum  lati- 
folium  and  Berula  angustifolia  with  their  al- 
lies, are  umbellifers,  which  bear  pinnate  instead 
of  bi-  or  tri-pinnate  leaves.  But  the  young 
plants  and  even  the  young  shoots  when  devel- 
oping from  the  rootstocks  under  water  comply 
with  the  above  rule,  producing  very  compound, 
finely  and  pectinately  dissected  leaves.  From  a 
systematic  point  of  view  these  leaves  indicate 
the  origin  of  the  water-parsnips  from  ordinary 
umbellifers,  which  generally  have  bi-  and  tri- 
pinnate  leaves. 

Similar  cases  of  double  adaptation,  depend- 
ent on  external  conditions  at  different  periods 
of  the  evolution  of  the  plant  are  very  numerous. 
They  are  most  marked  among  leguminous 
plants,  as  shown  by  the  trifoliolate  leaves  of  the 
thorn-broom  and  allies,  which  in  the  adult  state 
have  green  twigs  destitute  of  leaves. 

As  an  additional  instance  of  dimorphism  and 
probable  double  adaptation  to  unrecognized  ex- 


458  Ever-sporting  Varieties 

ternal  conditions  I  might  point  to  the  genns 
Acacia.  As  we  have  seen  in  a  previous 
lecture  some  of  the  numerous  species  of  this 
genus  bear  bi-pinnate  leaves,  while  others 
have  only  flattened  leaf-stalks.  According  to 
the  prevailing  systematic  conceptions,  the 
last  must  have  been  derived  from  the  first  by 
the  loss  of  the  blades  and  the  corresponding 
increase  of  size  and  superficial  extension  of  the 
stalk.  In  proof  of  this  view  they  exhibit,  as  we 
have  described,  the  ancestral  characters  in  the 
young  plantlets,  and  this  production  of  bi-pin- 
nate leaves  has  probably  been  retained  at  the  pe- 
riod of  the  corresponding  negative  mutations, 
because  of  some  distinct,  though  still  unknown 
use. 

Summarizing  the  results  of  this  discussion, 
we  may  state  that  useful  dimorphism,  or  dou- 
ble adaptation,  is  a  substitution  of  characters 
quite  analogous  to  the  useless  dimorphism  of 
cultivated  ever-sporting  varieties  and  the  stray 
occurrence  of  hereditary  monstrosities.  The 
same  laws  and  conditions  prevail  in  both  cases. 


E.  MUTATIONS 
Lecture  XVI 

THE  ORIGIN  OF  THE  PELORIC  TOAD-FLAX 

I  have  tried  to  show  previously  that  species,  in 
the  ordinary  sense  of  the  word,  consist  of  dis- 
tinct groups  of  units.  In  systematic  works 
these  groups  are  all  designated  by  the  name  of 
varieties,  but  it  is  usually  granted  that  the 
units  of  the  system  are  not  always  of  the  same 
value.  Hence  we  have  distinguished  between 
elementary  species  and  varieties  proper.  The 
first  are  combined  into  species  whose  common 
original  type  is  now  lost  or  unknown,  and  from 
their  characters  is  derived  an  hypothetical  im- 
age of  what  the  common  ancestor  is  supposed 
to  have  been.  The  varieties  proper  are  derived 
in  most  cases  from  still  existing  types,  and 
therefore  are  subjoined  to  them.  A  closer  in- 
vestigation has  shown  that  this  derivation  is 
ordinarily  produced  by  the  loss  of  some  definite 
attribute,  or  by  the  re-acquisition  of  an  appar- 

459 


460  Mutations 

ently  lost  character.  The  elenientary  species, 
on  the  other  hand,  must  have  arisen  by  the  pro- 
duction of  new  qualities,  each  new  acquisition 
constituting  the  origin  of  a  new  elementary 
form. 

Moreover  we  have  seen,  that  such  improve- 
ments and  such  losses  constitute  sharp  limits 
between  the  single  unit-forms.  Every  type,  of 
course,  varies  around  an  average,  and  the  ex- 
tremes of  one  form  may  sometimes  reach  or 
even  overlap  those  of  the  nearest  allies,  but 
the  offspring  of  the  extremes  always  return  to 
the  type.  The  transgression  is  only  temporary 
and  a  real  transition  of  one  form  to  another 
does  not  come  within  ordinary  features  of  fluc- 
tuating variability.  Even  in  the  cases  of  ever- 
sporting  varieties,  where  two  opposite  types 
are  united  within  one  race,  and  where  the  suc- 
ceeding individuals  are  continually  swinging 
from  one  extreme  to  the  other,  passing  through 
a  wide  range  of  intermediate  steps,  the  limits 
of  the  variety  are  as  sharply  defined  and  as  free 
from  real  transgression  as  in  any  other  form. 

In  a  complete  systematic  enumeration  of  the 
real  units  of  nature,  the  elementary  species  and 
varieties  are  thus  observed  to  be  discontinous 
and  separated  by  definite  gaps.  Every  unit 
may  have  its  youth,  may  lead  a  long  life  in  the 
adult  state  and  may  finally  die.     But  through 


Origin  of  Peloric  Toadflax  461 

the  whole  period  of  its  existence  it  remains  the 
same,  at  the  end  as  sharply  defined  from  its 
nearest  allies  as  in  the  beginning.  Should 
some  of  the  units  die  out,  the  gaps  between  the 
neighboring  ones  will  become  wider,  as  must 
often  have  been  the  case.  Such  segregations, 
however  important  and  useful  for  systematic 
distinctions,  are  evidently  only  of  secondary 
value,  when  considering  the  real  nature  of  the 
units  themselves. 

We  may  now  take  up  the  other  side  of  the 
problem.  The  question  arises  as  to  how  species 
and  varieties  have  originated.  According  to 
the  Darwinian  theory  they  have  been  produced 
from  one  another,  the  more  highly  differenti- 
ated ones  from  the  simpler,  in  a  graduated 
series  from  the  most  simple  forms  to  the  most 
complicated  and  most  highly  organized  exist- 
ing types.  This  evolution  of  course  must  have 
been  regular  and  continuous,  diverging  from 
time  to  time  into  new  directions,  and  linking 
all  organisms  together  into  one  common  pedi- 
gree. All  lacunae  in  our  present  system  are  ex- 
plained by  Darwin  as  due  to  the  extinction  of 
the  forms,  which  previously  filled  them. 

Since  Lamarck  first  propounded  the  concep- 
tion of  a  common  origin  for  all  living  beings, 
much  has  been  done  to  clear  up  our  ideas  as  to 
the  real  nature  of  this  process.     The  broader 


-1:62  Mutations 

aspect  of  the  subject,  including  the  general  pedi- 
gree of  the  ammal  and  vegetable  kingdom,  may 
be  said  to  have  been  outlined  by  Darwin  and  his 
followers,  but  this  phase  of  the  subject  lies  be- 
yond the  limits  of  our  present  discussion. 

The  other  phase  of  the  problem  is  concerned 
with  the  manner  in  which  the  single  elementary 
species  and  varieties  have  sprung  from  one  an- 
other. There  is  no  reason  to  suppose  that  the 
world  is  reaching  the  end  of  its  development, 
and  so  we  are  to  infer  that  the  production  of 
new  species  and  varieties  is  still  going  on.  In 
reality,  new  forms  are  observed  to  originate 
from  time  to  time,  both  wild  and  in  cultivation, 
and  such  facts  do  not  leave  any  doubt  as  to  their 
origin  from  other  allied  types,  and  according  to 
natural  and  general  laws. 

In  the  wild  state  however,  and  even  with  cul- 
tivated plants  of  the  field  and  garden,  the  condi- 
tions, though  allowing  of  the  immediate  obser- 
vation of  the  origination  of  new  forms,  are  by  no 
means  favorable  for  a  closer  inquiry  into  the 
real  nature  of  the  process.  Therefore  I  shall 
postpone  the  discussion  of  the  facts  till  an- 
other lecture,  as  their  bearing  will  be  more 
easily  understood  after  having  dealt  with  more 
complete  cases. 

These  can  only  be  obtained  by  direct  experi- 
mentation.     Comparative    studies,    of   course, 


Origin  of  Peloric  Toadflax  463 

are  valuable  for  the  elucidation  of  general  prob- 
lems and  broad  features  of  the  whole  pedigree, 
but  the  narrower  and  more  practical  question  as 
to  the  genetic  relation  of  the  single  foi-ms  to  one 
another  must  be  studied  in  another  way,  by 
direct  experiment.  The  exact  methods  of  the 
laboratory  must  be  used,  and  in  this  case  the 
garden  is  the  laboratory.  The  cultures  must 
be  guarded  with  the  strictest  care  and  every 
precaution  taken  to  exclude  opportunities  for 
error.  The  parents  and  grandparents  and  their 
offspring  must  be  kept  pure  and  under  control, 
and  all  facts  bearing  upon  the  birth  or  origin  of 
the  new  types  should  be  carefully  recorded. 

Two  great  difficulties  have  of  late  stood  in 
the  way  of  such  experimental  investigation. 
One  of  them  is  of  a  theoretical,  the  other  of  a 
practical  nature.  One  is  the  general  belief  in 
the  supposed  slowness  of  the  process,  the  other 
is  the  choice  of  adequate  material  for  experi- 
mental purposes.  Darwin's  hypothesis  of  nat- 
ural selection  as  the  means  by  which  new  types 
arise,  is  now  being  generally  interpreted  as 
stating  the  slow  transformation  of  ordinary 
fluctuating  divergencies  from  the  average  type 
into  specific  differences.  But  in  doing  so  it  is 
overlooked  that  Quetelet's  law  of  fluctuating 
variability  was  not  yet  discovered  at  the  time, 
when  Darwin  propounded  his  theory.     So  there 


464:  Mutations 

is  no  real  and  intimate  connection  between  these 
two  great  conceptions.  Darwin  frequently 
pointed  out  that  a  long  period  of  time  might  be 
needed  for  slow  improvements,  and  was  also  a 
condition  for  the  occurrence  of  rare  sports.  In 
any  case  those  writers  have  been  in  error,  ac- 
cording to  my  opinion,  who  have  refrained  from 
experimental  work  on  the  origin  of  species,  on 
account  of  this  narrow  interpretation  of  Dar- 
win's views.  The  choice  of  the  material  is 
quite  another  question,  and  obviously  all  de- 
pends upon  this  choice.  Promising  instances 
must  be  sought  for,  but  as  a  rule  the  best  way 
is  to  test  as  many  plants  as  possible.  Many  of 
them  may  show  nothing  of  interest,  but  some 
might  lead  to  the  desired  end. 

For  to-day's  lecture  I  have  chosen  an  in- 
stance, in  which  the  grounds  upon  which  the 
choice  was  based  are  very  evident.  It  is  the 
origin  of  the  peloric  toad-flax  (Lmaria  vulgaris 
peloria). 

The  ground  for  this  choice  lies  simply  in  the 
fact  that  the  peloric  toad-flax  is  known  to  have 
originated  from  the  ordinary  type  at  different 
times  and  in  different  countries,  under  more  or 
less  divergent  conditions.  It  had  arisen  from 
time  to  time,  and  hence  I  presumed  that  there 
was  a  chance  to  see  it  arise  again.  If  this 
should    happen    under    experimental    circum- 


Origin  of  Peloric  Toadflax  465 

stances  the  desired  evidence  might  easily  be 
gathered.  Or,  to  put  it  in  other  words,  we  must 
try  to  arrange  things  so  as  to  be  present  at  the 
time  when  nature  produces  another  of  these 
rare  changes. 

There  was  still  another  reason  for  choosing 
this  plant  for  observational  work.  The  step  from 
the  ordinary  toad-flax  to  the  peloric  form  is 
short,  and  it  appears  as  if  it  might  be  produced 
by  slow  conversion.  The  ordinary  species  pro- 
duces from  time  to  time  stray  peloric  flowers. 
These  occur  at  the  base  of  the  raceme,  or  rarely 
in  the  midst  of  it.  In  other  species  they  are 
often  seen  at  the  summit.  Terminal  pelories 
are  usually  regular,  having  five  equal  spurs. 
Lateral  pelories  are  generally  of  zygomorphic 
structure,  though  of  course  in  a  less  degree  than 
the  normal  bilabiate  flowers,  but  they  have  un- 
equal spurs,  the  middle  one  being  of  the  ordi- 
nary length,  the  two  neighboring  being  shorter, 
and  those  standing  next  to  the  opposite  side  of 
the  flower  being  the  shortest  of  all.  This  curi- 
ous remainder  of  the  original  symmetrical 
structure  of  the  flower  seems  to  have  been  over- 
looked hitherto  by  the  investigators  of  peloric 
toad-flaxes. 

The  peloric  variety  of  this  plant  is  character- 
ized by  its  producing  only  peloric  flowers.  No 
single  bilabiate  or  one-spurred  flower  remains. 


466  Mutations 

I  once  had  a  lot  of  nearly  a  hundred  spedmens 
of  this  fine  variety,  and  it  was  a  most  curious 
and  beautiful  sight  to  observe  the  many  thou- 
sands of  nearly  regular  flowers  blooming  at  the 
same  time.  Some  degree  of  variability  was  of 
course  present,  even  in  a  large  measure.  The 
number  of  the  spurs  varied  between  four  and  six, 
transgressing  these  limits  in  some  instances,  but 
never  so  far  as  to  produce  really  one-spurred 
flowers.  Comparing  this  variety  with  the  ordi- 
nary type,  two  ways  of  passing  over  from  the 
one  to  the  other  might  be  imagined.  One  would 
entail  a  slow  increase  of  the  number  of  the 
peloric  flowers  on  each  plant,  combined  with  a 
decrease  of  the  number  of  the  normal  ones,  the 
other  a  sudden  leap  from  one  extreme  to  the 
other  without  any  intermediate  steps.  The 
latter  might  easily  be  overlooked  in  field  obser- 
vations and  their  failure  may  not  have  the  value 
of  direct  proof.  They  could  never  be  over- 
looked, on  the  other  hand,  in  experimental  cul- 
ture. 

The  first  record  of  the  peloric  toad-flax  is  that 
of  Zioberg,  a  student  of  Linnaeus,  who  found  it 
in  the  neighborhood  of  Upsala.  This  curious 
discovery  was  described  by  Kudberg  in  his  dis- 
sertation in  the  year  1744.  Soon  afterwards 
other  localities  were  discovered  by  Link  near 
Gottingen  in  Germany  about  1791  and  after- 


Origin  of  Peloric  Toadflax  467 

wards  in  the  vicinity  of  Berlin,  as  stated  by 
Ratzeburg,  1825.  Many  other  localities  have 
since  been  indicated  for  it  in  Europe,  and  in  my 
own  country  some  have  been  noted  of  late,  as 
for  instance  near  Zandvoort  in  1874  and  near 
Oldenzaal  in  1896.  In  both  these  last  named 
cases  the  peloric  form  arose  spontaneously  in 
places  which  had  often  been  visited  by  botanists 
before  the  recorded  appearance,  and  therefore, 
without  any  doubt,  they  must  have  been  pro- 
duced directly  and  independently  by  the  ordi- 
nary species  which  grows  in  the  locality.  The 
same  holds  good  for  other  occurrences  of  it. 

In  many  instances  the  variety  has  been  re- 
corded to  disappear  after  a  certain  lapse  of 
time,  the  original  specimens  dying  out  and  no 
new  ones  being  produced.  Linaria  is  a  peren- 
nial herb,  multiplying  itself  easily  bj^  buds  grow- 
ing on  the  roots,  but  even  with  this  means  of 
propagation  its  duration  seems  to  have  definite 
limits. 

There  is  one  other  important  point  arguing 
strongly  for  the  independent  appearance  of  the 
peloric  form  in  its  several  localities.  It  is  the 
difficulty  of  fertilization  and  the  high  degree  of 
sterility,  even  if  artificially  pollinated.  Bees  and 
hmnble-bees  are  unable  to  crawl  into  the  nar- 
row tubular  flowers,  and  to  bring  the  fertilizing 
pollen  to  the  stigma.     Ripe  capsules  with  seeds 


468  Mutations 

have  never  been  seen  in  the  wild  state.  The 
only  writer  who  sueceeded  in  sowing  seeds  of 
the  peloric  variety  was  Wildenow  and  he  got 
only  very  few  seedlings.  But  even  in  artificial 
pollination  the  result  is  the  same,  the  anthers 
seeming  to  be  seriously  affected  by  the  change. 
I  tried  both  self-fertilization  and  cross-pollina- 
tion, and  only  with  utmost  care  did  I  succeed 
in  saving  barely  a  hundred  seeds.  In  order 
to  obtain  them  I  was  compelled  to  operate  on 
more  than  a  thousand  flowers  on  about  a  dozen 
peloric  plants. 

The  variety  being  wholly  barren  in  nature, 
the  assumption  that  the  plants  in  the  different 
recorded  localities  might  have  a  common  origin 
is  at  once  excluded.  There  must  have  been  at 
least  nearly  as  many  mutations  as  localities. 
This  strengthens  the  hope  of  seeing  such  a  mu- 
tation happen  in  one's  own  garden.  It  should 
also  be  remembered  that  peloric  flowers  are 
known  to  have  originated  in  quite  a  number 
of  different  species  of  Linaria,  and  also  with 
many  of  the  allied  species  within  the  range  of 
the  Lahiatiflorae. 

I  will  now  give  the  description  of  my  own  ex- 
periment. Of  course  this  did  not  give  the  ex- 
pected result  in  the  first  year.  On  the  contrary, 
it  was  only  after  eight  years'  work  that  I  had 
the  good  fortune  of  observing  the  mutation. 


Origin  of  Peloric  Toadflax  469 

But  as  the  whole  life-history  of  the  preceding 
generations  had  been  carefully  observed  and 
recorded,  the  exact  interpretation  of  the  fact 
was  readily  made. 

My  culture  commenced  in  the  year  1886.  I 
chose  some  plants  of  the  normal  type  with  one 
or  two  peloric  flowers  besides  the  bilabiate  ma- 
jority which  I  found  on  a  locality  in  the  neigh- 
borhood of  Hilversum  in  Holland.  I  planted 
the  roots  in  my  garden  and  from  them  had  the 
first  flowering  generation  in  the  following  sum- 
mer. From  their  seeds  I  grew  the  second  gen- 
eration in  three  following  years.  They  flow- 
ered profusely  and  produced  in  1889  only  one, 
and  in  1890  only  two  peloric  structures.  I  saved 
the  seeds  in  1889  and  had  in  1890-1891  the  third 
generation.  These  plants  likewise  flowered 
only  in  the  second  year,  and  gave  among  some 
thousands  of  symmetrical  blossoms,  only  one 
five-spurred  flower.  I  pollinated  this  flower 
myself,  and  it  produced  abundant  fruit  with 
enough  seeds  for  the  entire  culture  in  1892,  and 
they  only  were  sown. 

Until  this  year  my  generations  required  two 
years  each,  owing  to  the  perennial  habit  of  the 
plants.  In  this  way  the  prospects  of  the  cul- 
ture began  to  decrease,  and  I  proposed  to  try  to 
heighten  my  chances  by  having  a  new  genera- 
tion yearly.    With  this  intention  I  sowed  the 


470  Mutations 

selected  seeds  in  a  pan  in  the  glasshouse  of  my 
laboratory  and  planted  them  out  as  soon  as  the 
young  stems  had  reached  a  length  of  some  few 
centimeters.  Each  seedling  was  put  in  a  sepa- 
rate pot,  in  heavily  manured  soil.  The  pots 
were  kept  under  glass  until  the  beginning  of 
June,  and  the  young  plants  produced  during 
this  period  a  number  of  secondary  stems  from 
the  curious  hypocotylous  buds  which  are  so 
characteristic  of  the  species.  These  stems 
grew  rapidly  and  as  soon  as  they  were 
strong  enough,  the  plants  were  put  into 
the  beds.  They  all,  at  least  nearly  all, 
some  twenty  specimens,  flowered  in  the  follow- 
ing month. 

I  observed  only  one  peloric  flower  among  the 
large  number  present.  I  took  the  plant  bearing 
this  flower  and  one  more  for  the  culture  of  the 
following  year,  and  destroyed  all  others.  These 
two  plants  grew  on  the  same  spot,  and  were  al- 
lowed to  fertilize  each  other  by  the  agency  of 
the  bees,  but  were  kept  isolated  from  any  other 
congener.  They  flowered  abundantly,  but  pro- 
duced only  one-spurred  bilabiate  flowers  during 
the  whole  summer.  They  matured  more  than 
10  cu.  cm.  of  seeds. 

It  is  from  this  pair  of  plants  that  my  peloric 
race  has  sprung.  And  as  they  are  the  ancestors 
of  the  first  closely  observed  case  of  peloric  mu- 


Origin  of  Peloric  Toadflax  471 

tation,  it  seems  worth  while  to  give  some  details 
regarding  their  fertilization. 

Isolated  plants  of  Linaria  vulgaris  do  not 
produce  seed,  even  if  freely  pollinated  by  bees. 
Pollen  from  other  plants  is  required.  This  re- 
quirement is  not  at  all  restricted  to  the  genus 
Linaria,  as  many  instances  are  known  to  occur 
in  different  families.  It  is  generally  assumed 
that  the  pollen  of  any  other  individual  of  the 
same  species  is  capable  of  producing  fertiliza- 
tion, although  it  is  to  be  said  that  a  critical 
examination  has  been  made  in  but  few  instances. 

This,  however,  is  not  the  case,  at  least  not  in 
the  present  instance.  I  have  pollinated  a  num- 
ber of  plants,  grown  from  seed  of  the  same 
strain  and  combined  them  in  pairs,  and  ex- 
cluded the  visits  of  insects,  and  pollen  other 
than  that  of  the  plant  itself  and  that  of  the  spec- 
imen with  which  it  was  paired.  The  result  was 
that  some  pairs  were  fertile  and  others  barren. 
Counting  these  two  groups  of  pairs,  I  found 
them  nearly  equal  in  number,  indicating  there- 
by that  for  any  given  individual  the  pollen  of 
half  of  the  others  is  potent,  but  that  of  the  other 
half  impotent.  From  these  facts  we  may  con- 
clude the  presence  of  a  curious  case  of  dimor- 
phy,  analogous  to  that  proposed  for  the  prim- 
roses, but  without  visible  differentiating  marks 
in  the  flowers.     At  least  such  opposite  charac- 


472  Mutations 

ters  have  as  yet  not  been  ascertained  in  the  case 
of  our  toad-flax. 

In  order  to  save  seed  from  isolated  plants  it  is 
necessary,  for  this  reason,  to  have  at  least  two 
individuals,  and  these  must  belong  to  the  two 
physiologically  different  types.  Now  in  the 
year  1892,  as  in  other  years,  my  plants,  though 
separated  at  the  outset  by  distances  of  about  20 
cm.  from  each  other,  threw  out  roots  of  far 
greater  length,  growing  in  such  a  way  as  to 
abolish  the  strict  isolation  of  the  individuals. 
Any  plot  may  produce  several  stems  from  such 
roots,  and  it  is  manifestly  impossible  to  decide 
whether  they  all  belong  to  one  original  plant  or 
to  the  mixed  roots  of  several  individuals.  No 
other  strains  were  grown  on  the  same  bed  with 
my  plants  however,  and  so  I  considered  all  the 
stems  of  the  little  group  as  belonging  to  one 
plant.  But  their  perfect  fertility  showed,  ac- 
cording to  the  experience  described,  that  there 
must  have  been  at  least  two  specimens  mingled 
together. 

Returning  now  to  the  seeds  of  this  pair  of 
plants,  I  had,  of  course,  not  the  least  occasion 
to  ascribe  to  it  any  higher  value  than  the  har- 
vest of  former  years.  The  consequence  was 
that  I  had  no  reason  to  make  large  sowings,  and 
grew  only  enough  young  plants  to  have  about 
50  in  bloom  in  the  summer  of  1894.     Among 


Origin  of  Peloric  Toadflax  473 

these,  stray  peloric  flowers  were  observed  in 
somewhat  larger  number  than  in  the  previous 
generations,  11  plants  bearing  one  or  two, 
or  even  three  such  abnormalities.  This  how- 
ever, could  not  be  considered  as  a  real  advance, 
since  such  plants  may  occur  in  varying,  though 
ordinarily   small  numbers  in  every  generation. 

Besides  them  a  single  plant  was  seen  to  bear 
only  peloric  flowers ;  it  produced  racemes  on  sev- 
eral stems  and  their  branches.  All  were  peloric 
without  exception.  I  kept  it  through  the  winter, 
taking  care  to  preserve  a  complete  isolation  of 
its  roots.  The  other  plants  were  wholly  de- 
stroyed. Such  annihilation  must  include  both 
the  stems  and  roots  and  the  latter  of  course  re- 
quires considerable  labor.  The  following  year, 
however,  gave  proof  of  the  success  of  the  opera- 
tion, since  my  plant  bloomed  luxuriously  for  the 
second  time  and  remained  true  to  the  type  of 
the  first  year,  producing  peloric  flowers  ex- 
clusively. 

Here  we  have  the  first  experimental  mutation 
of  a  normal  into  a  peloric  race.  Two  facts  were 
clear  and  simple.  The  ancestry  was  known  for 
over  a  period  of  four  generations,  living  under 
the  ordinary  care  and  conditions  of  an  experi- 
mental garden,  isolated  from  other  toad-flaxes, 
but  freely  fertilized  by  bees  or  at  times  by  my- 
self.    This  ancestry  was  quite  constant  as  to 


474  Mutations 

the  peloric  peculiarity,  remaining  true  to  the 
wild  type  as  it  occurs  everywhere  in  my  country, 
and  showing  in  no  respect  any  tendency  to  the 
production  of  a  new  variety. 

The  mutation  took  place  at  once.  It  was  a 
sudden  leap  from  the  normal  plants  with  very 
rare  peloric  flowers  to  a  type  exclusively 
peloric.  No  intermediate  steps  were  observed. 
The  parents  themselves  had  borne  thousands  of 
flowers  during  two  summers,  and  these  were 
inspected  nearly  every  day,  in  the  hope  of  find- 
ing some  pelories  and  of  saving  their  seed  sep- 
arately. Only  one  such  flower  was  seen.  If 
there  had  been  more,  say  a  few  in  every  hun- 
dred flowers,  it  might  be  allowable  to  consider 
them  as  previous  stages,  showing  a  preparation 
of  the  impending  change.  But  nothing  of  this 
kind  was  observed.  There  was  simply  no  vis- 
ible preparation  for  the  sudden  leap. 

This  leap,  on  the  other  hand,  was  full  and 
complete.  No  reminiscence  of  the  former  con- 
dition remained.  Not  a  single  flower  on  the 
mutated  plant  reverted  to  the  previous  type. 
All  were  thoroughly  affected  by  the  new  attri- 
bute, and  showed  the  abnormally  augmented 
number  of  spurs,  the  tubular  structure  of  the 
corolla  and  the  round  and  narrow  entrance  of 
its  throat.  The  whole  plant  departed  absolute- 
ly from  the  old  type  of  its  progenitors. 


Origin  of  Pelorlc  Toadflax  475 

Three  ways  were  open  to  continue  my  exper- 
iment. The  first  was  indicated  by  the  abundant 
harvest  from  the  parent-plants  of  the  mutation. 
It  seemed  possible  to  compare  the  numerical 
proportion  of  the  mutated  seeds  with  those 
of  normal  plants.  In  order  to  ascertain 
this  proportion  I  sowed  the  greatest  part  of 
my  10  cu.  cm.  of  seed  and  planted  some  2000 
young  plants  in  little  pots  with  well-manured 
soil.  I  got  some  1750  flowering  plants  and  ob- 
served among  them  16  wholly  peloric  individ- 
uals. The  numerical  proportion  of  the  muta- 
tion was  therefore  in  this  instance  to  be 
calculated  equal  to  about  1^  of  the  whole  crop. 

This  figure  is  of  some  importance.  For  it 
shows  that  the  chance  of  finding  mutations 
requires  the  cultivation  of  large  groups  of  indi- 
viduals. One  plant  in  each  hundred  may  mu- 
tate, and  cultures  of  less  than  a  hundred  speci- 
mens must  therefore  be  entirely  dependent  on 
chance  for  the  appearance  of  new  forms,  even 
if  such  should  accidentally  have  been  produced 
and  lay  dormant  in  the  seed.  In  other  cases 
mutations  may  be  more  numerous,  or  on  the 
contrary,  more  rare.  But  the  chance  of  muta- 
tive changes  in  larger  numbers  is  manifestly 
much  reduced  by  this  experiment,  and  they  may 
be  expected  to  form  a  very  small  proportion  of 
the  culture. 


476  Mutations 

The  second  question  which  arose  from  the 
above  result  was  this.  Could  the  mutation  be 
repeated?  Was  it  to  be  ascribed  to  some  latent 
cause  which  might  be  operative  more  than 
once?  Was  there  some  hidden  tendency  to  muta- 
tion, which,  ordinarily  weak,  was  strengthened 
in  my  cultures  by  some  unknown  influence? 
Was  the  observed  mutation  to  be  explained  by 
a  common  cause  with  the  other  cases  recorded 
by  field-observations?  To  answer  this  question 
I  had  only  to  continue  my  expermient,  exclud- 
ing the  mutated  individuals  from  any  inter- 
crossing with  their  brethren.  To  this  end  I 
saved  the  seeds  from  duly  isolated  groups 
in  different  years  and  sowed  them  at  dif- 
ferent times.  For  various  causes  I  was  not 
prepared  to  have  large  cultures  from  these 
seeds,  but  notwithstanding  this,  the  mutation 
repeated  itself.  In  one  instance  I  obtained 
two,  in  another,  one  peloric  plant  with  exclusive- 
ly many-spurred  flowers.  As  is  easily  under- 
stood, these  were  related  as  ^'  nieces  "  to  the 
first  observed  mutants.  They  originated  in 
quite  the  same  way,  by  a  sudden  leap,  without 
any  preparation  and  without  any  intermediate 
steps. 

Mutation  is  proved  by  this  experience  to  be 
of  an  iterative  nature.  It  is  the  expression  of 
some  concealed  condition,  or  as  it  is  generally 


Origin  of  Peloric  Toadflax  477 

called,  of  some  liidden  tendency.  The  real 
nature  of  this  state  of  the  hereditary  qualities 
is  as  yet  wholly  unknown.  It  would  not  be  safe 
to  formulate  further  conclusions  before  the  evi- 
dence offered  by  the  evening-primroses  is 
considered. 

Thirdly,  the  question  arises,  whether  the 
mutation  is  complete,  not  only  as  to  the  mor- 
phologic character,  but  also  as  to  the  hered- 
itary constitution  of  the  mutated  individuals. 
But  here  unfortunately  the  high  degree  of  ster- 
ility of  the  peloric  plants,  as  previously  noted, 
makes  the  experimental  evidence  a  thing  of 
great  difficulty.  During  the  course  of  several 
years  I  isolated  and  planted  together  the 
peloric  individuals  already  mentioned,  all  in  all 
some  twenty  plants.  Each  individual  was  nearly 
absolutely  sterile  when  treated  with  its  own 
pollen,  and  the  aid  of  insects  was  of  no  avail. 
I  intercrossed  my  plants  artificially,  and 
pollinated  more  than  a  thousand  flowers.  Not 
a  single  one  gave  a  normal  fruit,  but  some  small 
and  nearly  rudimentary  capsules  were  pro- 
duced, bearing  a  few  seeds.  From  these  I  had 
119  flowering  plants,  out  of  which  106  were 
peloric  and  13  one-spurred.  The  great  major- 
ity, some  90^,  were  thus  shown  to  be  true  to 
their  new  type.  Whether  the  10;^  reverting 
ones  were  trulv  atavists,  or  whether  thev  were 


478  Mutations 

only  vicinists,  caused  by  stray  pollen  grains 
from  another  culture,  cannot  of  course  be  de- 
cided with  sufficient  certitude. 

Here  I  might  refer  to  the  observations  con- 
cerning the  invisible  dimorj)hous  state  of  the 
flowers  of  the  normal  toad-flax.  Individuals  of 
the  same  type,  when  fertilized  with  each  other, 
are  nearly,  but  not  absolutely,  sterile.  The 
yield  of  seeds  of  my  peloric  plants  agrees  fairly 
well  with  the  harvest  which  I  have  obtained 
from  some  of  the  nearly  sterile  pairs  of  indi- 
viduals in  my  former  trial.  Hence  the  sugges- 
tion is  forced  upon  us  that  perhaps,  owing  to 
some  unknown  cause,  all  the  peloric  individuals 
of  my  experiment  belonged  to  one  and  the  same 
type,  and  were  sterile  for  this  reason  only.  If 
this  is  true,  then  it  is  to  be  presumed  that  all 
previous  investigators  have  met  the  same  con- 
dition, each  having  at  hand  only  one  of  the  two 
required  types.  And  this  discussion  has 
the  further  advantage  of  showing  the  way, 
in  which  perhaps  a  full  and  constant  race  of 
peloric  toad-flaxes  may  be  obtained.  Two  indi- 
viduals of  different  type  are  required  to  start 
from.  They  seem  as  yet  never  to  have  arisen 
from  one  group  of  mutations.  But  if  it  were 
possible  to  combine  the  products  of  two  muta- 
tions obtained  in  different  countries  and  under 
different  conditions,  there  would  be  a  chance 


Origin  of  Peloric  Toadflax  479 

that  they  might  belong  to  the  supposed  opposite 
types,  and  thus  be  fertile  with  one  another. 

My  peloric  plants  are  still  available,  and  the 
occurrence  of  this  form  elsewhere  would  give 
material  for  a  successful  experiment.  The 
probability  thereof  is  enhanced  by  the  experi- 
ence that  my  peloric  plants  bear  large  capsules 
and  a  rich  harvest  of  seeds  when  fertilized  from 
plants  of  the  normal  one-spurred  race,  while 
they  remain  nearly  wholly  barren  by  artificial 
fertilization  with  others.  I  suppose  that  they 
are  infertile  with  the  normal  toad-flaxes  of  their 
own  sexual  disposition,  but  fertile  with  those  of 
the  opposite  constitution.  At  all  events  the 
fact  that  they  may  bear  abundant  seed  when 
properly  pollinated  is  an  indication  of  success- 
ful experiments  on  the  possibility  of  gaining  a 
hereditary  race  with  exclusively  peloric  flowers. 
And  such  a  race  would  be  a  distinct  gain  for 
sundry  physiologic  inquiries,  and  perhaps  not 
wholly  destitute  of  value  from  an  horticultural 
point  of  view. 

Returning  now  to  the  often  recorded  occur- 
rence of  peloric  toad-flaxes  in  the  wild  state  and 
recalling  our  discussion  about  the  improb- 
ability of  a  dispersion  from  one  locality  to 
another  by  seed,  and  the  probability  of  inde- 
pendent origin  for  most  of  these  cases,  we  are 
confronted  with  the  conception  that  a  latent 


480  Mutations 

tendency  to  mutation  must  be  universally 
present  in  the  whole  species.  Another  observa- 
tion, although  it  is  of  a  negative  character, 
gains  in  importance  from  this  point  of  view. 
I  refer  to  the  total  lack  of  intermediate  steps 
between  normal  and  peloric  individuals.  If 
such  links  had  ordinarily  been  produced  pre- 
vious to  the  purely  peloric  state  they  would  no 
doubt  have  been  observed  from  time  to  time. 
This  is  so  much  the  more  probable  as  Linaria 
is  a  perennial  herb,  and  the  ancestors  of  a 
mutation  might  still  be  in  a  flowering  condi- 
tion together  with  their  divergent  offspring. 
But  no  such  intermediates  are  on  record.  The 
peloric  toad-flaxes  are,  as  a  rule,  found  sur- 
rounded by  the  normal  type,  but  without  inter- 
grading  forms.  This  discontinuity  has  already 
been  insisted  upon  by  Hofmeister  and  others, 
even  at  the  time  when  the  theory  of  descent  was 
most  under  discussion,  and  any  link  would 
surely  have  been  produced  as  a  proof  of  a  slow 
and  continuous  change.  But  no  such  proof  has 
been  found,  and  the  conclusion  seems  admissible 
that  the  mutation  of  toad-flaxes  ordinarily,  if 
not  universally,  takes  place  by  a  sudden  step. 
Our  experiment  may  simply  be  considered  as  a 
thoroughly  controlled  instance  of  an  often  re- 
curring phenomenon.     It  teaches  us  how,  in  the 


Origin  of  Peloric  Toadflax  481 

main,  the  peloric  mutations  must  be  assumed  to 
proceed. 

This  conception  may  still  be  broadened.  We 
may  include  in  it  all  similar  occurrences,  in 
allied  and  other  species.  There  is  hardly  a 
limit  to  the  possibilities  which  are  opened  up  by 
this  experience.  But  it  will  be  well  to  refrain 
from  hazardous  theorizing,  and  consider  only 
those  cases  which  may  be  regarded  as  exact 
repetitions  of  the  same  phenomenon  and  of 
which  our  culture  is  one  of  the  most  recent  in- 
stances on  record.  We  will  limit  ourselves  to 
the  probable  origin  of  peloric  variations  at 
large,  of  which  little  is  known,  but  some  evi- 
dence may  be  derived  from  the  recorded  facts. 
Only  one  case  can  be  said  to  be  directly  analo- 
gous to  our  observations. 

This  refers  to  the  peloric  race  of  the  coromon 
snapdragon,  or  Antirrhinum  majus  of  our  gar- 
dens. It  is  known  to  produce  peloric  races  from 
time  to  time  in  the  same  way  as  does  the  toad- 
flax. But  the  snapdragon  is  self-fertile  and  so 
is  its  peloric  variety.  Some  cases  are  rela- 
tively old,  and  some  of  them  have  been  recorded 
and  in  part  observed  by  Darwin.  Whence  they 
have  sprung  and  in  what  manner  they  were 
produced,  seems  never  to  have  been  noted. 
Others  are  of  later  origin,  and  among  these  one 
or  two  varieties  have  been  accidentally  pro- 


482  Mutations 

duced  in  the  nursery  of  Mr.  Clir.  Lorenz  in 
Erfurt,  and  are  now  for  sale,  the  seeds  being 
guaranteed  to  yield  a  large  proportion  of 
peloric  individuals.  The  peloric  form  in  this 
case  appeared  at  once,  but  was  not  isolated,  and 
was  left  free  to  visiting  insects,  which  of  course 
crossed  it  with  the  surrounding  varieties. 
Without  doubt  the  existence  of  two  color-varie- 
ties of  the  peloric  type,  one  of  a  very  dark  red, 
indicating  the  ^'  Black  prince  "  variety  as  the 
pollen-parent,  and  the  other  with  a  white  tube 
of  the  corolla,  recalling  the  form  known  as 
' '  Delila, ' '  is  due  to  these  crossings.  I  had  last 
year  (1903)  a  large  lot  of  plants,  partly  normal 
and  partly  peloric,  but  evidently  of  hybrid 
origin,  from  seeds  from  this  nursery,  showing 
moreover  all  intermediate  steps  between  nearly 
wholly  peloric  individuals  and  apparently  nor- 
mal ones.  I  have  saved  the  seeds  of  the  iso- 
lated types  and  before  seeing  the  flowers  of 
their  offspring,  nothing  can  be  said  about  the 
purity  and  constancy  of  the  type,  when  freed 
from  hybrid  admixtures.  The  peloric  snap- 
dragon has  five  small  unequal  spurs  at  the  base 
of  its  long  tube,  and  in  this  respect  agrees  with 
the  peloric  toad-flax. 

Other  pelories  are  terminal  and  quite  regular, 
and  occur  in  some  species  of  Linaria,  where  I 
observed    them    in    Linaria    dalmatica.       The 


Origin  of  Peloric  Toadflax         483 

terminal  flowers  of  many  branches  were  large 
and  beautifully  peloric,  bearing  five  long  and 
equal  spurs.  About  their  origin  and  inher- 
itance nothing  is  known. 

A  most  curious  terminal  pelory  is  that  of  the 
common  foxglove  or  Digitalis  purpurea.  As  we 
have  seen  in  a  previous  lecture,  it  is  an  old 
variety.  It  was  described  and  figured  for  the 
first  time  by  Vrolik  of  Amsterdam,  and  the 
original  specimens  of  his  plates  are  still  to  be 
seen  in  the  collections  of  the  botanic  garden  of 
that  university.  Since  his  time  it  has  been 
propagated  by  seed  as  a  commercial  variety, 
and  may  be  easily  obtained.  The  terminal 
flower  of  the  central  stem  and  those  of  the 
branches  only  are  affected,  all  other  flowers 
being  wholly  normal.  Almost  always  it  is  ac- 
companied by  other  deviations,  among  which  a 
marked  increase  of  the  number  of  the  parts  of 
the  corolla  and  other  whorls  is  the  most  strik- 
ing. Likewise  supernumerary  petals  on  the 
outer  side  of  the  corolla,  and  a  production  of  a 
bud  in  the  center  of  the  capsule  may  be  often 
met  with.  This  bud  as  a  rule  grows  out  after 
the  fading  away  of  the  flower,  bursting  through 
the  green  carpels  of  the  unripe  fruit,  and  pro- 
ducing ordinarily  a  secondary  raceme  of  flow- 
ers. This  raceme  is  a  weak  but  exact  repetition 
of  the  first,  bearing  symmetrical  foxgloves  all 


484  Mutations 

along  and  terminating  in  a  peloric  structure. 

On  the  branches  these  anomalies  are  more  or 
less  reduced,  according  to  the  strengi:h  of  the 
branch,  and  conforming  to  the  rule  of  perio- 
dicity, given  in  our  lecture  on  the  ' '  five-leaved  ' ' 
clover.  Through  all  this  diminution  the  peloric 
type  remains  unchanged  and  therefore  becomes 
so  much  the  purer,  the  weaker  the  branches  on 
which  it  stands. 

I  am  not  sure  whether  such  peloric  flowers 
have  ever  been  purely  pollinated  and  their  seed 
saved  separately,  but  I  have  often  observed 
that  the  race  comes  pure  from  the  seed  of  the 
zygomorjDhic  flowers.  It  is  as  yet  doubtful 
whether  it  is  a  half  race  or  a  double  race,  and 
whether  it  might  be  purified  and  strengthened 
by  artificial  selection.  Perhaps  the  determina- 
tion of  the  hereditary  percentage  de- 
scribed when  dealing  with  the  tricotyls  might 
give  the  clue  to  the  acquisition  of  a  higher 
specialized  race.  The  variety  is  old  and  widely 
disseminated,  but  must  be  subjected  to  quite  a 
number  of  additional  experiments  before  it  can 
be  said  to  be  sufficiently  understood. 

The  most  widespread  peloric  variety  is  that 
of  gloxinia.  It  has  erect  instead  of  drooping 
flowers;  and  with  the  changed  position  the 
structure  is  also  changed.  Like  other  pelories 
it  has  five  equal  stamens  instead  of  four  un- 


Origin  of  Peloric  Toadflax  485 

equal  ones,  and  a  corolla  with  five  equal  seg- 
ments instead  of  an  upper  and  a  lower  lip.  It 
shows  the  peloric  condition  in  all  of  its  flowers 
and  is  often  combined  with  a  small  increase 
of  the  number  of  the  parts  of  the  whorls. 
It  is  for  sale  under  the  name  of  erecta,  and 
may  be  had  in  a  wide  range  of  color-types.  It 
seems  to  be  quite  constant  from  seed. 

Many  other  instances  of  peloric  flowers  are 
on  record.  Indian  cress  or  Tropaeolum  majus 
loses  the  spur  in  some  double  varieties  and 
with  it  most  of  its  symmetrical  structure;  it 
seems  to  be  considered  justly  as  a  peloric  mal- 
formation. Other  species  produce  such  anom- 
alies only  from  time  to  time  and  nothing  is 
known  about  their  hereditary  tendency.  One 
of  the  most  curious  instances  is  the  terminal 
flower  of  the  raceme  of  the  common  laburnum, 
which  loses  its  whole  papilionaceous  character 
and  becomes  as  regularly  quinate  as  a  common 
buttercup. 

Some  families  are  more  liable  to  pelorism 
than  others.  Obviously  all  the  groups,  the 
flowers  of  which  are  not  symmetrical,  are  to  be 
excluded.  But  then  we  find  that  labiates  and 
their  allies  among  the  dicotyledonous  plants, 
and  orchids  among  the  monocotyledonous  ones 
are  especially  subjected  to  this  alteration.  In 
both  groups  many  genera  and  a  long  list  of  spe- 


486  Mutations 

cies  could  be  quoted  as  proof.  The  family  of  the 
labiates  seems  to  be  essentially  rich  in  terminal 
pelories,  as  for  instance  in  the  wild  sage  or 
Salvia  and  the  dead-nettle  or  Lamium.  Here 
the  pelories  have  long  and  straight  corolla- 
tubes,  which  are  terminated  by  a  whorl  of  four 
or  ^VQ  segments.  Such  forms  often  occur  in 
the  wild  state  and  seem  to  have  a  geographic 
distribution  as  narrowlv  circumscribed  as  in 
the  case  of  many  small  species.  Those  of  the 
labiates  chiefly  belong  to  southern  Europe  and 
are  unknown  at  least  in  some  parts  of  the  other 
countries.  On  the  contrary  terminal  pelories 
of  Scropliularia  nodosa  are  met  with  from  time 
to  time  in  Holland.  Such  facts  clearly  point 
to  a  common  origin,  and  as  only  the  terminal 
flowers  are  affected  by  the  malformation,  the 
fertility  of  the  whole  plant  is  evidently  not  seri- 
ously infringed  upon. 

Before  leaving  the  labiates,  we  may  cite 
a  curious  instance  of  pelorism  in  the  toad-flax, 
which  is  quite  different  from  the  ordinary 
peloric  variety.  This  latter  may  be  considered 
from  a  morphologic  standpoint  to  be  owing  to 
a  five-fold  repetition  of  the  middle  part  of  the 
underlip.  This  conception  would  at  once  ex- 
plain the  occurrence  of  ^ve  spurs  and  of  the 
orange  border  all  around  the  corolla-tube.  We 
might  readily  imagine  that  any  other  of  the  five 


Origin  of  Pelortc  Toadflax  487 

parts  of  the  corolla  could  be  repeated  five-fold, 
in  which  case  there  would  be  no  spur,  and  no 
orange  hue  on  the  upper  corolla-ring.  Such 
forms  really  occur,  though  they  seem  to  be  more 
rare  than  the  five-spurred  pelories.  Very  little 
is  known  about  their  frequency  and  hereditary 
qualities. 

Orchids  include  a  large  number  of  peloric 
monstrosities  and  moreover  a  wild  pelory 
which  is  systematically  described  not  only  as  a 
separate  species  but  even  as  a  new  genus.  It 
bears  the  name  of  Uropedium  lindenii,  and  is 
so  closely  related  to  Ci/pripedium  caudatum 
that  many  authors  take  it  for  the  peloric  variety 
of  this  plant.  It  occurs  in  the  wild  state  in 
som-e  parts  of  Mexico,  where  the  Cypripedium 
also  grows.  Its  claims  to  be  a  separate  genus 
are  lessened  by  the  somewhat  monstrous  con- 
dition of  the  sexual  organs,  which  are  described 
as  quite  abnormal.  But  here  also,  interme- 
diates are  lacking,  and  this  fact  points  to  a 
sudden  origin. 

Many  cases  of  pelorism  afford  promising  ma- 
terial for  further  studies  of  experimental  muta- 
tions. The  peloric  toad-flax  is  only  the  proto- 
type of  what  may  be  expected  in  other  cases. 
No  opportunity  should  be  lost  to  increase  the  as 
yet  too  scanty  evidence  on  this  point. 


Lectuke  XVII 

THE   PRODUCTION  OF  DOUBLE  FLOWERS 

Mutations  occur  as  often  among  cultivated 
plants  as  among  those  in  the  wild  state.  Gar- 
den flowers  are  known  to  vary  markedly. 
Much  of  their  variability,  however,  is  due  to 
hybridism,  and  the  combination  of  characters 
previously  separate  has  a  value  for  the  breeder 
nearly  equal  the  production  of  really  new  qual- 
ities. Nevertheless  there  is  no  doubt  that  some 
new  characters  appear  from  time  to  time. 

In  a  previous  lecture  we  have  seen  that 
varietal  characters  have  many  features  in  com- 
mon. One  of  them  is  their  frequent  recur- 
rence both  in  the  same  and  in  other,  often  very 
distantly  related,  species.  This  recurrence  is  an 
important  factor  in  the  choice  of  the  material 
for  an  experimental  investigation  of  the  nature 
of  mutations. 

Some  varieties  are  reputed  to  occur  more 
often  and  more  readily  than  others.  White-col- 
ored varieties,  though  so  very  common,  seem  for 
the  most  part  to  be  of  ancient  date,  but  only  few 

488 


Production  of  Double  Flowers         489 

have  a  known  origin,  however.  Without  any 
doubt  many  of  them  have  been  found  in  a  wild 
state  and  were  introduced  into  culture.  On  the 
other  hand  double  flowers  are  exceedingly  rare 
in  the  wild  state,  and  even  a  slight  indication  of 
a  tendency  towards  doubling,  the  stray  petaloid 
stamens,  are  only  rarely  observed  growing  wild. 
In  cultivation,  however,  double  flowers  are  of 
frequent  occurrence ;  hence  the  conclusion  that 
they  have  been  produced  in  gardens  and  nur- 
series more  frequently  than  perhaps  any  other 
type  of  variety. 

In  the  beginning  of  my  experimental  work  I 
cherished  the  hope  of  being  able  to  produce  a 
white  variety.  My  experiments,  however,  have 
not  been  successful,  and  so  I  have  given  them 
up  temporarily.  Much  better  chances  for  a 
new  double  variety  seemed  to  exist,  and  my  en- 
deavors in  this  direction  have  finally  been 
crowned  with  success. 

For  this  reason  I  jDropose  to  deal  now  with 
the  production  of  double  flowers,  to  inquire 
what  is  on  record  about  them  in  horticultural 
literature,  and  to  give  a  full  description  of  the 
origin  thereof  in  an  instance  which  it  was  my 
good  fortune  to  observe  in  my  garden. 

Of  course  the  historical  part  is  only  a  hasty 
survey  of  the  question  and  will  only  give  such 
evidence  as  may  enable  us  to  get  an  idea  of  the 


492  Mutations 

of  a  later  period.  A  long  list  could  easily  be 
made,  to  show  that  during  the  whole  history  of 
horticulture  double  varieties  have  arisen 
from  time  to  time.  As  far  as  we  can  judge, 
such  appearances  have  been  isolated  and  sud- 
den. Sometimes  they  sprang  into  existence  in 
the  full  display  of  their  beauty,  but  most  com- 
monly they  showed  themselves  for  the  first  time, 
exhibiting  only  spare  supernumerary  petals. 
Whenever  such  sports  were  worked  up,  a  few 
years  sufficed  to  reach  the  entire  development 
of  the  new  varietal  attribute. 

From  this  superficial  survey  of  historical 
facts,  the  inference  is  forced  upon  us  that  the 
chance  of  producing  a  new  double  variety  is 
good  enough  to  justify  the  attempt.  It  has  fre- 
quently succeeded  for  practical  purposes,  why 
should  it  not  succeed  as  well  for  purely  scien- 
tific investigation?  At  all  events  the  type  rec- 
ommends itself  to  the  student  of  nature,  both 
on  account  of  its  frequency,  and  of  the  apparent 
insignificance  of  the  first  step,  combined  with 
the  possibility  of  rapidly  working  up  from  this 
small  beginning  of  one  superfluous  petal  to- 
wards the  highest  degree  of  duplication. 

Compared  with  the  tedious  experimental  pro- 
duction of  the  peloric  toad-flax,  the  attempt  to 
produce  a  double  flower  has  a  distinct  attrac- 
tion.    The  peloric  toad-flax  is  nothing  new ;  the 


Production  of  Double  Flowers         493 

experiment  was  only  a  repetition  of  what  pre- 
sumably takes  place  often  within  the  same 
species.  To  attempt  to  produce  a  double 
variety  we  may  choose  any  species,  and  of 
course  should  select  one  which  as  yet  has  not 
been  known  to  produce  double  flowers.  By 
doing  so  we  will,  if  we  succeed,  produce  some- 
thing new.  Of  course,  it  does  not  matter 
whether  the  new  variety  has  an  horticultural  in- 
terest or  not,  and  it  seems  preferable  to  choose 
a  wild  or  little  cultivated  species,  to  be  quite 
sure  that  the  variety  in  question  is  not  already 
in  existence.  Finally  the  prospect  of  success 
seems  to  be  enhanced  if  a  species  is  chosen,  the 
nearest  allies  of  which  are  known  to  have  pro- 
duced double  flowers. 

For  these  reasons  and  others  I  chose  for  my 
experiment  the  corn-marigold,  or  Chrysanthe- 
mum segetum.  It  is  also  called  the  golden  corn- 
flower. In  the  wheat  and  rye  fields  of  central 
Europe  it  associates  with  the  blue-bottle  or  blue 
corn-flower.  It  is  sometimes  cultivated  and  the 
seeds  are  offered  for  sale  by  many  nursery- 
men. It  has  a  cultivated  variety,  called  grandi- 
iiorum,  which  is  esteemed  for  its  brilliancy  and 
long  succession  of  golden  bloom.  This  variety 
has  larger  flower-heads,  surrounded  with  a 
fuller  border  of  ray-florets  the  species  belongs 
to  a  genus  many  species  of  which  have  pro- 


"494  Mutations 

duced  double  varieties.  One  of  them  is 
the  Japanese  marigold,  others  are  the  cari- 
natum  and  the  imhricatimi  species.  Nearly 
allied  are  quite  a  number  of  garden-plants  with 
double  flower-heads,  among  which  are  the 
double  camomiles. 

My  attention  was  first  drawn  to  the  structure 
of  the  heads  and  especially  to  the  number  of  the 
ray-florets  of  the  corn-marigold.  The  species 
appertains  to  that  group  of  composites  which 
have  a  head  of  small  tubular  florets  surrounded 
by  a  broad  border  of  rays.  These  rays,  when 
counted,  are  observed  to  occur  in  definite  num- 
bers, which  are  connected  with  each  other  by  a 
formula,  known  as  **  the  series  "  of  Braun  and 
Schimper.  In  this  formula,  which  commences 
with  1  and  2,  each  number  is  equal  to  the  sum 
of  the  two  foregoing  figures.  Thus  5,  8  and  13 
are  very  frequent  occurrences,  and  the  following 
number,  21,  is  a  most  general  one  for  apparent- 
ly full  rays,  such  as  in  daisies,  camomiles, ^rmca 
and  many  other  wild  and  cultivated  species. 

These  numbers  are  not  at  all  constant.  Thev 
are  only  the  averages,  around  which  the  real 
numbers  fluctuate.  There  mav  even  be  an  over- 
lapping  of  the  extremes,  since  the  fluctuation 
around  13  may  even  go  beyond  8  and 
21,  and  so  on.  But  such  extremes  are  only 
found  in  stray  flowers,  occurring  on  the  same 


Production  of  Double  Floivcrs  495 

individuals  with  tiie  lesser  degrees  of  deviation. 
Now  the  marigold  averages  13,  and  the 
grandiflorum  21  rays.  The  wild  speeies  is  pure 
in  this  respect,  but  the  garden-variety  is  not. 
The  seeds  which  are  offered  for  sale  usually 
contain  a  mixture  of  both  forms  and  theii* 
hybrids.  So  I  had  to  isolate  the  pure  types 
from  this  mixture  and  to  ascertain  their  con- 
stancy and  mutual  independency.  To  this  end 
I  isolated  from  the  mixture  first  the  13-rayed, 
and  afterwards  the  21-rayed  types.  As  the 
marigolds  are  not  sufficiently  self-fertile,  and 
are  not  easily  pollinated  artificially,  it  seemed 
impossible  to  carry  on  these  two  experiments  at 
the  same  time  and  in  the  same  garden.  I  de- 
voted the  first  three  vears  to  the  lower  form, 
isolated  some  individuals  with  12  -  13  rays  out  of 
the  mixture  of  1892  and  counted  the  ray-florets 
on  the  terminal  head  of  every  plant  of  the  en- 
suing generation  next  year.  I  cultivated  and 
counted  in  this  way  above  150  individuals  and 
found  an  average  of  exactly  13  with  compara- 
tively few  individuals  displaying  14  or  only  12 
rays,  and  with  the  remainder  of  the  plants 
grouped  symmetrically  around  this  average.  T 
continued  the  experiment  for  still  another  year 
and  found  the  same  group  of  figures.  T  was 
then  satisfied  as  to  the  purity  of  the  isolated 
strain.     Next  year  T  sowed  a  new  mixture  in 


496  Mutations 

order  to  isolate  the  reputed  pure  grandiflorum 
type.  During  the  beginning  of  the  flowering- 
period  I  ruthlessly  threw  away  all  plants  dis- 
playing less  than  21  rays  in  the  first  or  terminal 
head.  But  this  selection  was  not  to  be  consid- 
ered as  complete,  because  the  13-rayed  race  may 
eventually  transgress  its  boundary  and  come 
over  to  the  21  and  more.  This  made  a  second 
selection  necessary.  On  the  selected  plants 
all  the  secondary  heads  were  inspected  and 
their  ray-florets  counted.  Some  individuals 
showed  an  average  of  about  13  and  were  de- 
stroyed. Others  gave  doubtful  figures  and 
were  likewise  eliminated,  and  only  6  out  of  a 
lot  of  nearly  300  flowering  plants  reached  an 
average  of  21  for  all  of  the  flowers. 

Our  summer  is  a  short  one,  compared  with  the 
long  and  beautiful  summer  of  California,  and  it 
was  too  late  to  cut  off  the  faded  and  the  open 
flowers,  and  await  new  ones,  which  might  be 
purely  fertilized  after  the  destruction  of 
all  minor  plants.  So  I  had  to  gather  the  seed 
from  flowers,  which  might  have  been  partially 
fertilized  by  the  wrong  pollen.  This  however, 
is  not  so  great  a  drawback  in  selection  experi- 
ments as  might  be  supposed  at  first  sight.  The 
selection  of  the  following  year  is  sure  to  elim- 
inate the  offspring  of  such  impure  parentage. 


Production  of  Double  Flowers         497 

A  far  more  important  principle  is  that  of  the 
hereditary  percentage,  already  discussed  in  our 
lecture  on  the  selection  of  monstrosities.  In 
our  present  case  it  had  to  be  applied  only  to  the 
six  selected  plants  of  1895.  To  this  end  the  seeds 
of  each  of  them  were  sown  separately,  the  ray- 
florets  of  the  terminal  heads  of  each  of  the 
new  generation  were  counted,  and  curves  and 
averages  were  made  up  for  the  six  groups. 
Five  of  them  gave  proof  of  still  being  mixtures 
and  were  wholly  rejected.  The  children  of  the 
sixth  parent,  however,  formed  a  group  of  uni- 
form constitution,  all  fluctuating  around  the  de- 
sired average  of  21.  All  in  all  the  terminal 
heads  of  over  1500  plants  have  been  subjected 
to  the  somewhat  tedious  work  of  counting  their 
ray-florets.  And  this  not  in  the  laboratory,  but 
in  the  garden,  without  cutting  them  off.  Other- 
wise it  would  obviously  have  been  impossible  to 
recognize  the  best  plants  for  preservation.  I 
chose  only  two  plants  which  in  addition  recom- 
mended themselves  by  the  average  number  of 
rays  on  their  secondary  heads,  sowed  their 
seeds  next  year  separately  and  compared  the 
numerical  constitution  of  their  offspring. 
Both  groups  averaged  21  and  were  distributed 
very  symmetrically  around  this  mean.     This  re- 


498  Mutations 

suit  showed  that  no  further  selection  could  be 
of  any  avail,  and  that  I  had  succeeded  in  purify- 
ing the  21-rayed  grandiflorum  variety. 

It  is  from  this  grandiflorum  that  I  have  finally 
produced  my  double  variety.  In  the  year  1896 
I  selected  from  among  the  above  quoted  1500 
plants,  500  with  terminal  heads  bearing  21  or 
more  rays.  On  these  I  counted  the  rays  of  all 
the  secondary  heads  about  the  middle  of  August 
(1896)  and  found  that  they  had,  as  a  rule, 
retrograded  to  lower  figures.  On  many  thou- 
sands of  heads  only  two  were  found  having  22 
rays.  All  others  had  the  average  number  of  21 
or  even  less.  I  isolated  the  individual  which 
bore  these  two  heads,  allowed  them  to  be  fertil- 
ized by  insects  with  the  pollen  of  some  of  the 
best  plants  of  the  same  group,  but  destroyed  the 
remainder. 

This  single  exceptional  plant  has  been  the 
starting  point  of  my  double  variety.  It  was  not 
remarkable  for  its  terminal  head,  which  exhib- 
ited the  average  number  of  rays  of  the  21-rayed 
race.  Nor  was  it  distinguished  by  the  average 
figure  for  all  its  heads.  It  was  only  selected 
because  it  was  the  one  plant  which  had  some 
secondary  heads  with  one  ray  more  than  all  the 
others.  This  indication  was  very  slight,  and 
could  not  have  been  detected  save  by  the 
counting  of  the  rays  of  thousands  of  heads. 


Production  of  Double  Flowers         499 

But  the  rarity  of  the  anomaly  was  exactly  the 
indication  wanted,  and  the  same  deviation 
would  have  had  no  signification  whatever,  had  it 
occurred  in  a  group  fluctuating  symmetrically 
around  the  average  figure.  On  the  other  hand, 
the  observed  anomaly  was  only  an  indication, 
and  no  guarantee  of  future  developments. 

Here  it  should  be  remarked  that  the  indica- 
tion alluded  to  was  not  the  appearance  of  the 
expected  character  of  doubling  in  ever  so  slight 
a  measure.  It  was  only  a  guide  to  be  followed 
in  further  work.  The  real  character  of  double 
flower-heads  among  composites  lies  in  the  pro- 
duction of  rays  on  the  disk.  No  increase  of  the 
number  of  the  outer  rays  can  have  the  same  sig- 
nificance. A  hasty  inspection  of  double  flower- 
heads  may  convey  the  idea  that  all  rays  are  ar- 
ranged around  a  little  central  cluster  of  disk- 
florets,  the  remainder  of  the  original  disk.  But 
a  closer  investigation  will  always  reveal  the 
fallacy  of  this  conclusion.  Hidden  between 
the  inner  rays,  and  covered  by  them,  lie  the 
little  tubular  and  fertile  florets  everywhere 
on  the  disk.  Thev  mav  not  be  easilv  seen,  but 
if  the  supernumerary  raj^s  are  pulled  out,  the 
disk  may  be  seen  to  bear  numerous  small 
florets  at  intervals.  But  these  intervals 
are  not  at  all  numerous,  showing  thereby  that 
only  a  relatively  small  number  of  tubes  has  been 


500  Mutations 

converted  into  rays.  This  conversion  is  ob- 
viously the  true  mark  of  the  doubling,  and  be- 
fore traces  of  it  are  found,  no  assertion  what- 
ever can  be  given  as  to  the  issue  of  the  pedigree- 
experiment. 

Three  more  years  were  required  before  this 
first,  but  decisive  trace  was  discovered.  During 
these  years  I  subjected  my  strain  to  the  same 
sharp  selection  as  has  already  been  described. 
The  chosen  ancestor  of  the  race  had  flowered  in 
1896,  and  the  next  year  I  sowed  its  seeds  only. 
From  this  generation  I  chose  the  one  plant  with 
the  largest  number  of  rays  in  its  terminal  head, 
and  repeated  this  in  the  following  year. 

The  consequence  was  that  the  average  num- 
ber of  rays  increased  rapidly,  and  with  it  the 
absolute  maximum  of  the  whole  strain.  The 
average  came  up  from  21  to  34.  Brighter  and 
brighter  crowns  of  the  yellow  rays  improved 
my  race,  until  it  became  difficult  and  very  time- 
consuming  to  count  all  the  large  rays  of  the  bor- 
ders. The  largest  numbers  determined  in  the 
succeeding  generations  increased  by  leaps  from 
21  to  34  in  the  first  year,  and  thence  to  48  and  66 
in  the  two  succeeding  summers.  Every  year  I 
was  able  to  save  enough  seed  from  the  very  best 
plant  and  to  use  it  only  for  the  continuance  of 
the  race.  Before  the  selected  plants  were  al- 
lowed to  open  the  flowers  from  which  the  seed 


Production  of  Double  Flowers         501 

was  to  be  gathered,  nearly  the  whole  remaining 
culture  was  exterminated,  excepting  only  some 
of  the  best  examples,  in  order  to  have  the  re- 
quired material  for  cross-pollination  by  insects. 
Each  new  generation  was  thereby  as  sharply 
selected  as  possible  with  regard  to  both  parents. 
All  flower-heads  were  of  course  closely  in- 
spected. Not  the  slightest  indication  of  real 
doubling  was  discovered,  even  in  the  summer  of 
1899  in  the  fourth  generation  of  my  selected 
race.  But  among  the  best  the  new  character 
suddenh^  made  its  appearance.  It  was  at  the 
commencement  of  September  (1899),  too  late 
to  admit  of  the  seeds  ripening  before  win- 
ter. An  inspection  of  the  younger  heads 
was  made,  which  revealed  three  heads 
with  some  few  rays  in  the  midst  of  the  disk  on 
one  plant,  the  result  of  the  efforts  of  four  years. 
Had  the  germ  of  the  mutation  lain  hidden 
through  all  this  time!  Had  it  been  pres- 
ent, though  dormant  in  the  original  sample 
of  seed?  Or  had  an  entirely  new  creation  taken 
place  during  my  continuous  endeavors?  Per- 
haps as  their  more  or  less  immediate  re- 
sult? It  is  obviously  impossible  to  answer  these 
questions,  before  further  and  similar  experi- 
ments shall  have  been  performed,  bringing  to 
light  other  details  that  will  enable  us  to  reach  a 
more  definite  conclusion. 


502  Mutations 

The  fact  that  the  origination  of  such  forms 
is  accessible  to  direct  investigation  is  proven 
quite  independently  of  all  further  considera- 
tions. The  new  variety  came  into  existence  at 
once.  The  leap  may  have  been  made  by  the 
ancestor  of  the  year  1895,  or  by  the  plant  of 
1899,  which  showed  the  first  central  rays,  or 
the  sport  may  have  been  gradually  built  up  dur- 
ing those  four  years.  In  each  case  there  was  a 
leap,  contrasting  with  the  view  which  claims  a 
very  long  succession  of  years  for  the  develop- 
ment of  every  new  character. 

Having  discovered  this  first  trace  of  doubling, 
it  was  to  be  expected  that  the  new  variety  would 
be  at  once  as  pure  and  as  rich  as  other  double 
composites  usually  are.  Some  effect  of  the 
crossing  with  the  other  seed-bearing  individuals 
might  still  disturb  this  uniformity  in  the  follow- 
ing year,  but  another  year's  work  would  elim- 
inate even  this  source  of  impurity. 

These  two  years  have  given  the  expected  re- 
sult. The  average  number  of  the  rays,  which 
had  already  arisen  from  13  to  34  now  at  once 
came  up  to  47  and  55,  the  last  figure  being  the 
sum  of  21  and  34  and  therefore  the  probable 
uttermost  limit  to  be  reached  before  absolute 
doubling.  The  maximum  numbers  came  as  high 
as  100  in  1900,  and  reached  even  200  in  1901. 
Such  heads  are  as  completely  double  as  are  the 


Production  of  Double  Flowers         5Uo 

brightest  heads  of  the  most  beautiful  double 
commercial  varieties  of  composites.  Even  the 
best  white  camomiles  {Chrysanthemum  ino- 
dorum)  and  the  gold-flowers  or  garden-mari- 
golds {Calendida  officinalis)  do  not  come  nearer 
to  purity  since  they  always  have  scores  of  little 
tubular  florets  between  the  rays  on  their  disks. 

Real  atavists  or  real  reversionists  were  seen 
no  more  after  the  first  purification  of  the  race. 
I  have  continued  my  culture  and  secured  last 
summer  (1903)  as  many  and  as  completely 
doubled  heads  as  previously.  The  race  has  at 
once  become  permanent  and  constant.  It  has  of 
course  a  wide  range  of  fluctuating  variability, 
but  the  lower  limit  has  been  worked  up  to  about 
34  rays,  a  figure  never  reached  by  the  grandi- 
florum  parent,  from  which  my  new  variety  is 
thus  sharply  separated. 

Unfortunately  the  best  flowers  and  even  the 
best  individuals  of  my  race  are  wholly  barren. 
Selection  has  reached  its  practical  limit.  Seeds 
must  be  saved  from  less  dense  heads,  and  no 
way  has  been  found  of  avoiding  it.  The  ray- 
florets  are  sterile,  even  in  the  wild  species,  and 
when  growing  in  somewhat  large  numbers  on 
the  disk,  they  conceal  the  fertile  flowers  from 
the  visiting  insects,  and  cause  them  also  to  be 
sterile.  The  same  is  the  case  with  the  best  cul- 
tivated forms.     Their  showiest  individuals  are 


504  Mutations 

barren,  and  incapable  of  the  reproduction  of  tlie 
race. 

This  last  is  therefore,  of  necessity,  always 
continued  by  means  of  individuals  whose  devia- 
tion from  the  mean  average  is  the  least.  But 
in  many  cases  the  varieties  are  so  highly  dif- 
ferentiated that  selection  has  become  quite  su- 
perfluous for  practical  purposes.  I  have  al- 
ready discussed  the  question  as  to  the  actual 
moment,  in  which  the  change  of  the  grandiflor- 
um  variety  into  the  new  plenum  form  must  be 
assumed  to  have  taken  place.  In  this  respect 
some  stress  is  to  be  laid  on  the  fact  that  the  im- 
provement through  selection  has  been  gradual 
and  continuous,  though  very  rapid  from  the  first 
moment.  But  with  the  appearance  of  the  first 
stray  rays  within  the  disk,  this  continuity  sud- 
denly changed.  All  the  children  of  this  original 
mutated  plant  showed  the  new  character,  the 
rays  within  the  disk,  without  exception.  Not 
on  all  the  heads,  nor  even  on  the  majority  of  the 
heads  on  some  individuals,  but  on  some  heads  all 
gave  clear  proof  of  the  possession  of  the  new 
attribute.  This  was  present  in  all  the  repre- 
sentatives of  the  new  race,  and  had  never  been 
seen  in  any  of  their  parents  and  grandparents. 
Here  there  was  evidently  a  sudden  leap,  at 
least  in  the  external  form  of  the  plants.  And  it 
seems  to  me  to  be  the  most  simple  conception, 


Production  of  Double  Flowers         505 

that  this  visible  leap  directly  corresponded  to 
that  inner  change,  which  brought  about  the  com- 
plete inheritability  of  the  new  peculiarity.  It 
is  very  interesting  to  observe  how  completely 
my  experience  agrees  with  the  results  of  the 
observations  of  breeders  at  large.  No  doubt 
a  comparison  is  difficult,  and  the  circumstances 
are  not  adequate  to  a  close  study. 

Isolation  and  selection  have  been  applied  com- 
monly only  so  far  as  was  consistent  with  the  re- 
quirements of  practical  horticulture,  and  of 
course  a  determination  of  the  hereditary  per- 
centage was  never  made.  The  disregard  of  this 
feature  made  necessary  a  greater  length  of  time 
and  a  larger  number  of  generations  to  bring 
about  the  desired  changes.  Notwithstanding 
this,  however,  it  has  been  seen  that  double  va- 
rieties are  produced  suddenly.  This  may  have 
occurred  unexpectedly  or  after  a  few  years'  ef- 
fort toward  the  end  desired.  Whether  this 
sudden  appearance  is  the  consequence  of  a 
single  internal  differentiating  step,  or  of  the 
rapid  succession  of  lesser  changes,  cannot  yet 
be  made  out.  The  extreme  variability  of  dou- 
ble flowers  and  the  chance  of  their  appearance 
with  only  slight  indications  of  the  previous  pet- 
aloid  alterations  of  a  few  stamens  mav  often  re- 
suit  in  their  origin  being  overlooked,  while 
subsequent  generations  may  come  in  for  full  no- 


506  Mutations 

tice.  In  the  greater  number  of  cases  recorded 
it  remains  doubtful  whether  the  work  said  to  be 
done  to  obtain  a  new  double  variety  was  done 
before  the  appearance  of  these  preliminary  indi- 
cations or  afterward. 

In  the  first  case,  it  would  correspond  with 
our  selection  of  large  numbers  of  florets  in  the 
outer  rays,  in  the  second  however,  with  the  or- 
dinary purification  of  new  races  from  hybrid 
mixtures. 

In  scientific  selection-experiments  such  cross- 
es are  of  course  avoided,  and  the  process  of 
purification  is  unnecessary,  even  as  in  the 
Chrysanthemum  culture.  The  first  generation 
succeeding  the  original  plant  with  disk-rays  was 
in  this  respect  wholly  uniform  and  true  to  the 
new  type. 

In  practice  the  work  does  not  start  from  such 
slight  indications,  and  is  done  with  no  other 
purpose  in  view  than  to  produce  double  flowers 
in  species  in  which  they  did  not  already  exist. 
Therefore  it  is  of  the  highest  importance  to 
know  the  methods  used  and  the  chances  of  suc- 
cess. Unfortunately  the  evidence  is  very  scanty 
on  both  points. 

Lindlev  and  other  writers  on  horticultural 
theory  and  practice  assert  that  a  large  amount 
of  nourishment  tends  to  produce  double  flow- 
ers, while  a  culture  under  normal  conditions. 


Production  of  Double  Flowers         507 

even  if  the  plants  are  very  strong  and  healthy, 
has  no  such  effect.  But  even  here  it  remains 
doubtful  whether  it  applies  to  the  period  before 
or  after  the  internal  mutation.  On  the  other 
hand  success  is  not  at  all  to  be  relied  upon,  nor 
is  the  work  to  be  regarded  as  easy.  The  in- 
stances of  double  flowers  said  to  be  obtainable 
at  will,  are  too  rare  in  comparison  with  the 
number  of  cases,  where  the  first  indication  of 
them  was  found  accidentallv. 

Leaving  all  these  doubtful  points,  which  will 
have  to  be  cleared  up  by  further  scientific  in- 
vestigation, the  high  degree  of  variability  re- 
quires further  discussion.  It  may  be  considered 
from  three  different  points  of  view  according 
to  the  limit  of  the  deviation  from  the  average, 
to  the  dependency  on  external  conditions  and  to 
periodicity.  It  seems  best  to  take  up  the  last 
two  points  first. 

On  a  visit  to  a  nurserv  at  Erfurt  I  once  in- 
spected  an  experiment  with  a  new  double  varie- 
ty of  the  common  blue-bottle  or  blue  corn-flow- 
er. The  plants  were  dependent  on  the  weather 
to  a  high  degree.  Bad  weather  increased  the 
number  of  poorly  filled  flower-heads,  while 
warm  and  sunny  days  were  productive  of  beau- 
tiful double  flowers.  The  heads  that  are  borne 
by  strong  branches  have  a  greater  tendency  to 
become  double  than  those  of  the  weaker  ones. 


508  Mutations 

and  towards  the  autumn,  when  all  those  of  the 
first  group  are  faded  away,  and  only  a  weak 
though  large  section  of  the  heads  is  still  flower- 
ing, the  whole  aspect  of  the  variety  gradually 
retrogrades.  The  same  law  of  dependency  and 
periodicity  is  prevalent  everywhere.  In  my 
own  cultures  of  the  improved  field-marigold  I 
have  observed  it  frequently.  The  number  of  the 
ray-florets  may  be  considered  as  a  direct  re- 
sponse to  nourishment,  both  when  this  is  deter- 
mined by  external  circumstances,  and  when  it 
depends  on  the  particular  strength  of  the 
branch,  which  bears  the  head  in  question.  It  is 
a  case  exactly  similar  to  that  of  the  supernumer- 
ary carpels  of  the  pistilloid  poppy,  and  the  de- 
ductions arrived  at  with  that  variety  may  be 
applied  directly  to  double  flowers. 

This  dependency  upon  nourishment  is  of  high 
practical  importance  in  combination  with  the 
usual  effect  of  the  doubling  which  makes 
the  flowers  sterile.  It  is  a  general  rule  that  the 
most  perfect  flowers  do  not  produce  seed.  At 
the  height  of  the  flowering  period  the  external 
circumstances  are  the  most  favorable,  and  the 
flowering  branches  still  constitute  the  stronger 
axes  of  the  plants.  Hence  we  may  infer  that 
sterility  will  prevail  precisely  in  this  period. 
Many  varieties  are  known  to  yield  only  seeds 
from  the  very  last  flowers,  as  for  instance  some 


Production  of  Double  Flowers         509 

double  begonias.  Others  bear  only  seed  on  their 
weaker  lateral  branches,  as  the  double  camomile, 
or  become  fertile  only  towards  the  fall,  as  is 
often  the  case  with  the  above  quoted  Erfurt  va- 
riety of  the  blue-bottle.  As  far  as  I  have  been 
able  to  ascertain,  such  seeds  are  quite  adequate 
for  the  reproduction  and  perpetuation  of  the 
double  varieties,  but  the  question  whether  there 
are  differences  between  the  seeds  of  the  more 
or  less  double  flowers  of  the  same  plants  still 
remains  open.  It  is  very  probable,  from  a  the- 
oretical point  of  view,  that  such  differences  ex- 
ist, but  perhaps  they  are  so  slight,  as  to  have 
practically  no  bearing  on  the  question. 

On  the  ground  of  their  wide  range  of  varia- 
bility, the  double  varieties  must  be  regarded  as 
pertaining  to  the  group  of  ever-sporting  forms. 
On  one  side  thev  fluctuate  in  the  direction  to- 
wards  such  petalomanous  flowers  as  are  borne 
by  the  stocks  and  others,  which  we  have  pre- 
viously discussed.  Here  no  trace  of  the  fertile 
organs  is  left.  But  this  extreme  is  never  reach- 
ed by  petaloid  double  flowers.  A  gap  remains 
which,  often  overlooked,  always  exists,  and 
which  sharply  separates  the  two  types.  On  the 
other  hand  the  alteration  of  the  stamens  grad- 
ually relapses  to  perfectly  single  flowers.  Here 
the  analogy  with  the  pistillody  of  the  poppies 
and  with  the  ''  five-leaved  "  clover  is  obvious. 


510  Mutations 

This  conception  of  the  inner  nature  of  double 
flowers  explains  the  fact  that  the  varietal  mark 
is  seldom  seen  to  be  complete  throughout  larger 
groups  of  individuals,  providing  these  have  not 
been  already  selected  by  this  character. 
Tagetes  africana  is  liable  to  produce  some 
poorly  filled  specimens,  and  some  double  va- 
rieties of  carnations  are  offered  for  sale  with  the 
note  that  the  seed  yields  only  80%  of  doubles. 
With  Chrysanthemum  coronarium  and  blue-bot- 
tles this  figure  is  often  announced  to  be  only 
about  50^.  No  doubt  it  is  partly  due  to  im- 
purities, caused  by  vicinism,  but  it  is  obviously 
improbable  that  the  effect  of  these  impurities 
should  be  so  large. 

Some  cases  of  partial  reversion  may  be  inter- 
preted in  the  same  way.  Among  the  garden 
anemones,  Anemone  coronaria,  there  is  a  va- 
riety called  the  ^  *  Bride, ' '  on  account  of  its  pure 
white  flowers.  It  is  for  sale  with  single  and 
with  double  flowers,  and  these  two  forms  are 
known  to  sport  into  one  another,  although  they 
are  multiplied  in  the  vegetative  way.  Such  cases 
are  known  to  be  of  quite  ordinary  occurrence. 
Of  course  such  sports  must  be  considered  as 
partial,  and  the  same  stem  may  bear  both  types 
of  flowers.  It  even  happens  that  some  partic- 
ular flower  is  partly  double  and  partly  single. 
Mr.  Krelage,  of  Haarlem,  had  the  kindness  to 


Production  of  Double  Flowers         511 

send  me  such  a  curious  flower.  One  half  of  it 
was  completely  double,  while  the  other  half  was 
entirely  single,  bearing  normal  and  fertile  sta- 
mens in  the  ordinary  number. 

The  same  halfway  doubling  is  recorded  to 
occur  among  composites  sometimes,  and  from 
the  same  source  I  possess  in  my  collection  a 
head  of  Pyrethrum  roseum,  bearing  on  half  of 
its  disk  elongated  corolla  tubes,  and  on  the 
other  half  the  small  disk-florets  of  the  typical 
species. 

It  is  a  current  belief,  that  varieties  are  im- 
proved by  continued  culture.  I  have  never  been 
able  to  ascertain  the  grounds  on  which  this  con- 
viction rests.  It  may  be  referred  either  to  the 
purity  of  the  race  or  to  the  complete  develop- 
ment of  the  varietal  character.  In  the  first  case 
it  is  a  question  of  hybrid  mixtures  from  which 
many  young  varieties  must  be  freed  before  be- 
ing placed  on  the  market.  But  as  we  have  al- 
ready seen  in  a  former  lecture,  this  requires 
only  three  or  four  years,  and  afterwards  the 
degree  of  purit}^  is  kept  up  to  the  point  which 
proves  to  be  the  most  suitable  for  practical 
purposes.  The  complete  development  of  the 
varietal  character  is  a  question  restricted  to 
ever-sporting  varieties,  since  in  white  flowers 
and  other  constant  varieties  this  degree  is  va- 
riable in  a  very  small  and  unimportant  meas- 


512  Mutations 

lire.  Hence  the  double  flowers  seem  to  afford 
a  very  good  example  for  this  discussion. 

It  can  be  decided  by  two  facts.  First  by  a 
consideration  of  the  oldest  double  varieties,  and 
secondly  by  that  of  the  very  youngest.  Are  the 
older  ones  now  in  a  better  condition  than  at  the 
outset!  Have  they  really  been  gradually  im- 
proved during  the  centuries  of  their  existence? 
Obviously  this  can  only  be  answered  by  a  com- 
parison of  the  figures  given  by  older  writers, 
with  the  varieties  as  they  are  now  in  culture. 
Munting's  drawings  and  descriptions  are  now 
nearly  two  centuries  and  a  half  old,  but  I  do  not 
find  any  real  difference  between  his  double  va- 
rieties and  their  present  representatives.  So 
it  is  in  other  cases  in  which  improvements  by 
crossing  or  the  introduction  of  new  forms  does 
not  vitiate  the  evidence.  Double  varieties,  as 
a  rule,  are  exactly  the  same  now,  as  they  were 
at  the  time  of  their  first  introduction. 

If  this  were  otherwise  one  would  expect  that 
young  double  varieties  should  in  the  main  dis- 
play only  slight  grades  of  the  anomaly,  and 
that  they  would  require  centuries  to  reach  their 
full  development.  Nothing  of  the  kind  is  on 
record.  On  the  contrary  the  newest  double 
sorts  are  said  to  be  not  only  equal  to  their  prede- 
cessors, but  to  excel  them.  As  a  rule  such  claims 
may  be  exaggerated,  but  not  to  any  great  extent. 


Production  of  Double  Floivers         513 

This  is  proven  in  the  simplest  way  by  the  re- 
sult of  our  own  experiment. 

In  the  double  field-marigold  we  have  the  very 
first  generation  of  a  variety  of  pure  and  not 
hybrid  origin.  It  shows  the  new  attribute  in 
its  full  development.  It  has  flower-heads  near- 
ly as  completely  filled  as  the  best  double  varie- 
ties of  allied  cultivated  composites.  In  the  sec- 
ond generation  it  reached  heads  with  200  rays 
each,  and  much  larger  numbers  will  seldom  be 
seen  in  older  species  on  heads  of  equal  size.  I 
have  compared  my  novelty  with  the  choicest 
double  camomiles  and  others,  but  failed  to  dis- 
cover any  real  difference.  Improvement  of  the 
variety  developed  in  the  experiments  carried  on 
by  myself  seems  to  be  excluded  by  the  fact 
that  it  comes  into  conflict  with  the  same  difficul- 
ty that  confronts  the  older  cultivated  species, 
viz. :  the  increasing  sterility  of  the  race. 

It  is  perfectly  evident  that  this  double  mari- 
gold is  now  quite  constant.  Continuously  va- 
rying about  a  fixed  average  it  may  live  through 
centuries,  but  the  mean  and  the  limits  will  al- 
ways remain  the  same,  as  in  the  case  of  the 
ever-sporting  varieties. 

Throughout  this  lecture  I  have  spoken  of 
double  flowers  and  double  flower-heads  of  com- 
posites as  of  one  single  group.  They  are  as 
nearly  related  from  the  hereditary  point  of 


514  Mutations 

view,  as  they  are  divergent  in  other  respects. 
It  would  be  superfluous  to  dwell  any  longer 
upon  the  difference  between  heads  and  flowers. 
But  it  is  as  well  to  point  out,  that  the  term  dou- 
ble flowers  indicates  a  motley  assemblage  of  dif- 
ferent phenomena.  The  hen-and-chicken  daisy, 
and  the  corresponding  variety  of  the  garden- 
cineraria  (Cineraria  cruenta),  are  extremes  on 
one  side.  The  hen-and-chicken  type  occurs 
even  in  other  families  and  is  known  to  produce 
most  curious  anomalies,  as  with  Scabiosa,  the 
supernumerary  heads  of  which  may  be  pro- 
duced on  long  stalks  and  become  branched 
themselves  in  the  same  manner. 

Petalody  of  the  stamens  is  well  known  to  be 
the  ordinary  type  of  doubling.  But  it  is  often 
accompanied  by  a  multiplication  of  the  organs, 
both  of  the  altered  stamens  and  of  the  petals 
themselves.  This  proliferation  may  consist  in 
median  or  in  lateral  cleavages,  and  in  both 
cases  the  process  may  be  repeated  one  or  more 
times.  It  would  be  quite  superfluous  to  give 
more  details,  which  may  be  gathered  from  any 
morphologic  treatise  on  double  flowers.  But 
from  the  physiologic  point  of  view  all  these 
cases  are  to  be  considered  as  one  large  group, 
complying  with  previously  given  definitions  of 
the  ever-sporting  varieties.  They  are  very  va- 
riable and  wholly  permanent.     Obviously  this 


Production  of  Double  Flowers         515 

permanency  agrees  perfectly  with  the  concep- 
tion of  their  sudden  origin. 


Lecture  XVIII 

NEW  SPECIES  OF  OENOTHERA 

In  our  experiments  on  the  origin  of  peloric 
varieties  and  double  flowers  we  were  guided  in 
the  choice  of  our  material  by  a  survey  of  the 
evidence  already  at  hand.  We  chose  the  types 
known  to  be  most  commonly  produced  anew, 
either  in  the  wild  state  or  under  the  conditions 
of  cultivation.  In  both  instances  our  novelty 
was  a  variety  in  the  ordinary  sense  of  the  word. 
Our  pedigree-culture  was  mainly  an  experi- 
mental demonstration  of  the  validity  of  conclu- 
sions, which  had  previously  been  deduced  from 
such  observations  as  can  be  made  after  the  ac- 
cidental birth  of  new  forms. 

From  these  facts,  and  even  from  these  pedi- 
gree-experiments, it  is  scarcely  allowable  to 
draw  conclusions  as  to  the  origin  of  real  spe- 
cies. If  we  want  to  know  how  species  originate, 
it  is  obviously  necessary  to  have  recourse  to 
direct  observation.  The  question  is  of  the  high- 
est importance,  both  for  the  theory  of  descent, 
and  for  our  conception  of  the  real  nature  of 

516 


Neiv  Species  of  Oenothera  517 

systematic  affinities  at  large.  Many  authors 
have  tried  to  solve  it  on  the  ground  of  compara- 
tive studies  and  of  speculations  upon  the  bio- 
logic relations  of  plants  and  animals.  But  in 
vain.  Contradiction  and  doubt  still  reign  su- 
preme. All  our  hopes  now  rest  on  the  result  of 
experiments. 

Unfortunately  such  experiments  seemed  sim- 
ply impossible  a  few  years  ago.  What  is  to 
guide  us  in  the  choice  of  the  material?  The 
answer  may  only  be  expected  from  a  consid- 
eration of  elementary  species.  For  it  is  obvious 
that  they  only  can  be  observed  to  originate,  and 
that  the  systematic  species,  because  they  are 
only  artificial  groups  of  lower  unities,  can  never 
becom.e  the  subject  of  successful  experimental 
inquiry. 

In  previous  lectures  we  tried  to  clear  up  the 
differences  existing  between  nearly  related  ele- 
mentary species.  We  have  seen  that  they  af- 
fect all  of  the  attributes  of  the  plants,  each  of 
them  changing  in  some  measure  all  of  the  or- 
gans. Nevertheless  they  were  due  to  distinct 
unities  and  of  the  lowest  possible  degree.  Such 
unit-steps  may  therefore  be  expected  to  become 
visible  some  time  or  other  by  artificial  means. 
On  the  other  hand,  mutations  as  a  rule  make 
their  appearance  in  groups,  and  there  are  many 
systematic   species  which  on  close  inspection 


518  Mutations 

have  been  shown  to  be  in  reality  composite  as- 
semblages. Roses  and  brambles,  hawkweeds 
and  willows  are  the  best  known  examples.  Vio- 
lets and  Drab  a  verna,  dandelions  and  helian- 
themums  and  many  other  instances  were  dealt 
with  in  previous  lectures.  Even  wheat  and  bar- 
ley and  corn  afford  instances  of  large  groups 
of  elementary  species.  Formerly  mixed  in 
the  fields,  they  became  separated  during  the 
last  century,  and  now  constitute  constant  races, 
which,  for  brevity's  sake,  are  dealt  with  under 
the  name  of  varieties. 

In  such  groups  of  nearly  allied  forms  the  sin- 
gle members  must  evidently  be  of  common  or- 
igin. It  is  not  necessary  for  them  to  have  orig- 
inated all  in  the  same  place  or  at  the  same  time. 
In  some  cases,  as  with  Drab  a  verna,  the  present 
geographic  distribution  points  to  a  common 
birthplace,  from  whence  the  various  forms  may 
about  the  same  period  have  radiated  in  all  direc- 
tions. The  violets  on  the  other  hand  seem  to 
include  widely  diffused  original  forms,  from 
which  branches  have  started  at  different  times 
and  in  different  localities. 

The  origin  of  such  groups  of  allied  forms 
must  therefore  be  the  object  of  our  research. 
Perhaps  we  might  find  a  whole  group,  perhaps 
only  part  of  it.  In  my  opinion  we  have  the 
right  to  assume  that  if  Draba  and  violets  and 


New  Species  of  Oenothera  519 

others  have  formerly  mutated  in  this  way,  oth- 
er species  must  at  present  be  in  the  same 
changeable  condition.  And  if  mutations  in 
groups,  or  such  periodic  mutations  should  be 
the  rule,  it  is  to  be  premised  that  these  periods 
recur  from  time  to  time,  and  that  many  species 
must  even  now  be  in  mutating  condition,  while 
others  are  not. 

It  is  readily  granted  that  the  constant  condi- 
tion of  species  is  the  normal  one,  and  that  mu- 
tating periods  must  be  the  exception.  This  fact 
does  not  tend  to  increase  our  prospect  of  dis- 
covering a  species  in  a  state  of  mutability. 
Many  species  will  have  to  be  tested  before  find- 
ing an  instance.  On  the  other  hand,  a  direct  trial 
seems  to  be  the  only  way  to  reach  the  goal.  No 
such  special  guides  as  those  that  led  us  to  the 
choice  of  pelories  and  double  flowers  are  avail- 
able. The  only  indication  of  value  is  the  pre- 
sumption that  a  condition  of  mutability  might 
be  combined  with  a  general  state  of  variability 
at  large,  and  that  groups  of  plants  of  very  uni- 
form features  might  be  supposed  to  be  constant 
in  this  respect  too.  On  the  contrary,  anomalies 
and  deviations  if  existent  in  the  members  of 
one  strain,  or  found  together  in  one  native  lo- 
cality of  a  species,  might  be  considered  as  an 
indication  in  the  desired  direction. 

Few  plants  vary  in  the  wild  state  in  such  a 


520  Mutations 

measure  as  to  give  distinct  indications.  All  have 
to  be  given  a  trial  in  the  garden  under  conditions 
as  similar  as  possible  to  their  natural  environ- 
ments. Cultivated  plants  are  of  course  to  be 
excluded.  Practically  they  have  already  under- 
gone the  experience  in  question  and  can  not  be 
expected  to  change  their  habits  soon  enough. 
Moreover  they  are  often  of  hybrid  origin.  The 
best  way  is  to  experiment  with  the  native  plants 
of  one's  own  country. 

I  have  made  such  experiments  with  some  hun- 
dred species  that  grow  wild  in  Holland.  Some 
were  very  variable,  as  for  instance,  the  jointed 
charlock  (Raphanus  RapJianistrum)  and  the 
narrow-leaved  plantain  (Plantago  lanceolata) , 
Others  seemed  more  uniform,  but  many  species, 
collected  without  showing  any  malformation, 
subsequently  produced  them  in  my  garden, 
either  on  the  introduced  plants  themselves  or 
among  their  offspring.  From  this  initial  ma- 
terial I  have  procured  a  long  series  of  heredi- 
tary races,  each  with  some  peculiar  anomaly  for 
its  special  character.  But  this  result  was  only 
a  secondary  gain,  a  meager  consolation  for  the 
negative  fact  that  no  real  mutability  could  be 
discovered. 

My  plants  were  mostly  annuals  or  biennials, 
or  such  perennials  as  under  adequate  treatment 
might  produce  flowers  and  seeds  during  their 


New  Species  of  Oenothera  521 

first  summer.  It  would  be  of  no  special  use  to 
enumerate  them.  The  negative  result  does  not 
apply  to  the  species  as  such,  but  only  to  the  in- 
dividual strain,  which  I  collected  and  cultivated. 
Many  species,  which  are  quite  constant  with  us, 
may  be  expected  to  be  mutable  in  other  parts 
of  their  range. 

Only  one  of  all  my  tests  met  my  expectations. 
This  species  proved  to  be  in  a  state  of  mutation, 
producing  new  elementary  forms  continually, 
and  it  soon  became  the  chief  member  of  my  ex- 
perimental garden.  It  was  one  of  the  evening- 
primroses. 

Several  evening-primroses  have  at  different 
times  been  introduced  into  European  gardens 
from  America.  From  thence  they  have  spread 
into  the  vicinity,  becoming  common  and  exhibit- 
ing the  behavior  of  indigenous  types.  Oenoth- 
era biennis  was  introduced  about  1614  from 
Virginia,  or  nearly  three  centuries  ago.  0. 
muricata,  with  small  corollas  and  narrow 
leaves,  was  introduced  in  the  year  1789  by 
John  Hunneman,  and  0.  suaveolens,  or  sweet- 
scented  primrose,  a  form  very  similar  to  the 
biennis,  about  the  same  time,  in  1778,  by 
John  Fothergill.  This  form  is  met  with  in  dif- 
ferent parts  of  France,  while  the  biennis  and 
muricata  are  very  common  in  the  sandy  regions 
of  Holland,  where  I  have  observed  them  for 


522  Mutations 

more  than  40  years.  They  are  very  constant 
and  have  proven  so  in  my  experiments.  Be- 
sides these  three  species,  the  large-flowered 
evening-primrose,  or  Oenothera  lamarckiana, 
is  found  in  some  localities  in  Holland 
and  elsewhere.  We  know  little  concerning 
its  origin.  It  is  supposed  to  have  come 
from  America  in  the  same  way  as  its  con- 
geners, but  as  yet  I  have  not  been  able  to 
ascertain  on  what  grounds  this  supposition 
rests.  As  far  as  I  know,  it  has  not  been  seen 
growing  wild  in  this  country,  though  it  may 
have  been  overlooked.  The  fact  that  the 
species  of  this  group  are  subject  to  many  sys- 
tematic controversies  and  are  combined  by  dif- 
ferent writers  into  systematic  species  in  differ- 
ent ways,  being  often  considered  as  varieties 
of  one  or  two  types,  easily  accounts  for  it 
having  been  overlooked.  However,  it  would  be 
of  great  interest  to  ascertain  whether  0.  la- 
marckiana yet  grows  in  America,  and  whether 
it  is  in  the  same  state  of  mutability  here  as  it 
is  in  Holland. 

The  large-flowered  evening-primrose  was  also 
cultivated  about  the  beginning  of  the  last  cen- 
tury in  the  gardens  of  the  Museum  d'Histoire 
Naturelle,  at  Paris,  where  it  was  noticed  by 
Lamarck,  who  at  once  distinguished  it  as  an  un- 
described  species.    He  wrote  a  complete  descrip- 


New  Species  of  Oenothera  523 

tion  of  it  and  his  type  sjjecimens  are  still  pre- 
served in  the  herbarium  of  the  Museum,  where 
I  have  compared  them  with  the  plants  of  my 
own  culture.  Shortly  afterwards  it  was  re- 
named by  Seringe,  in  honor  of  its  eminent  dis- 
coverer, whose  name  it  now  bears.  So  Lamarck 
unconsciously  discovered  and  described  himself 
the  plant,  which  after  a  century,  was  to  become 
the  means  of  an  empirical  demonstration  of  his 
far-reaching  views  on  the  common  origin  of  all 
living  beings. 

Oenothera  lamarckiana  is  considered  in 
Europe  as  a  garden-plant,  much  prized  for 
parks  and  ornamental  planting.  It  is  cultivated 
by  seed-merchants  and  offered  for  sale.  It  has 
escaped  from  gardens,  and  having  abundant 
means  for  rapid  multiplication,  has  become  wild 
in  many  places.  As  far  as  I  know  its  known 
localities  are  small,  and  it  is  to  be  presumed 
that  in  each  of  them  the  plant  has  escaped  sep- 
arately from  culture.  It  was  in  this  state  that 
I  first  met  with  this  beautiful  species. 

Lamarck's  evening-primrose  is  a  stately 
plant,  with  a  stout  stem,  attaining  often  a  height 
of  1.6  meters  and  more.  When  not  crowded  the 
main  stem  is  surrounded  by  a  large  circle  of 
smaller  branches,  growing  upwards  from  its 
base  so  as  often  to  form  a  dense  bush.  These 
branches  in  their  turn  have  numerous  lateral 


524  Mutations 

branches.  Most  of  them  are  crowned  with 
flowers  in  summer,  which  regularly  succeed  each 
other,  leaving  behind  them  long  spikes  of  young 
fruits.  The  flowers  are  large  and  of  a  bright 
yellow  color,  attracting  immediate  attention, 
even  from  a  distance.  They  open  towards 
evening,  as  the  name  indicates,  and  are  pollin- 
ated by  humble-bees  and  moths.  On  bright  days 
their  duration  is  confined  to  one  evening,  but 
during  cloudy  weather  they  may  still  be  found 
open  on  the  following  morning.  Contrary  to 
their  congeners  they  are  dependent  on  visiting 
insects  for  pollination.  0.  biennis  and  0. 
muricata  have  their  stigmas  in  immediate  con- 
tact with  the  anthers  within  the  flower-buds,  and 
as  the  anthers  ojDen  in  the  morning  preceding 
the  evening  of  the  display  of  the  petals,  fecun- 
dation is  usually  accomplished  before  the  in- 
sects are  let  in.  But  in  0.  lamarckiana  no 
such  self-fertilization  takes  place.  The  stigmas 
are  above  the  anthers  in  the  bud,  and  as  the 
style  increases  in  length  at  the  time  of  the 
opening  of  the  corolla,  they  are  elevated  above 
the  anthers  and  do  not  receive  the  pollen.  Or- 
dinarily the  flowers  remained  sterile  if  not  vis- 
ited by  insects  or  pollinated  by  myself,  although 
rare  instances  of  self-fertilization  were  seen. 

In  falling  off,  the  flowers  leave  behind  them 
a  stout  ovary  with  four  cells  and  a  large  number 


'New  Species  of  Oenothera  525 

of  young  seeds.  The  capsule,  when  ripe,  opens 
at  its  summit  with  four  valves,  and  contains 
often  from  two  to  three  hundred  seeds.  A  hun- 
dred capsules  on  the  main  stem  is  an  average 
estimate,  and  the  lateral  branches  may  ripen 
even  still  more  fruits,  b}^  which  a  very  rapid  dis- 
semination is  ensured. 

This  striking  species  was  found  in  a  locality 
near  Hilversum,  in  the  vicinity  of  Amsterdam, 
where  it  grew  in  some  thousands  of  individuals. 
Ordinarily  biennial,  it  produces  rosettes  in  the 
first,  and  stems  in  the  second  year.  Both  the 
stems  and  the  rosettes  were  at  once  seen  to  be 
highly  variable,  and  soon  distinct  varieties 
could  be  distinguished  among  them. 

The  first  discovery  of  this  locality  was  made 
in  1886.  Afterwards  I  visited  it  many  times, 
often  weekly  or  even  daily  during  the  first  few 
years,  and  always  at  least  once  a  year  up  to 
the  present  time.  This  stately  plant  showed  the 
long-sought  peculiarity  of  producing  a  number 
of  new  species  everv  vear.  Some  of  them  were 
observed  directly  on  the  field,  either  as  stems 
or  as  rosettes.  The  latter  could  be  transplanted 
into  my  garden  for  further  observation,  and 
the  stems  vielded  seeds  to  be  sown  under  like 
control.  Others  were  too  weak  to  live  a  suffi- 
ciently long  time  in  the  field.  They  were  dis- 
covered by  sowing  seed  from  indifferent  plants 


526  Mutations 

of  the  wild  locality  in  tlie  garden.  A  third 
and  last  method  of  getting  still  more  new  spe- 
cies from  the  original  strain,  was  the  repetition 
of  the  sowing  process,  by  saving  and  sowing 
the  seed  which  ripened  on  the  introduced 
plants.  These  various  methods  have  led  to  the 
discovery  of  over  a  dozen  new  types,  never  pre- 
viously observed  or  described. 

Leaving  the  physiologic  side  of  the  rela- 
tions of  these  new  forms  for  the  next  lecture, 
it  would  be  profitable  to  give  a  short  descrip- 
tion of  the  several  novelties.  To  this  end  they 
may  be  combined  under  five  different  heads,  ac- 
cording to  their  systematic  value.  The  first 
head  includes  those  which  are  evidently  to  be 
considered  as  varieties,  in  the  narrower  sense 
of  the  word,  as  previously  given.  The  second 
and  third  heads  indicate  the  real  progressive 
elementary  species,  first  those  which  are  as 
strong  as  the  parent-species,  and  secondly  a 
group  of  weaker  types,  apparently  not  destined 
to  be  successful.  Under  the  fourth  head  I  shall 
include  some  inconstant  forms,  and  under  the 
last,  head  those  that  are  organically  incomplete. 

Of  varieties  with  a  negative  attribute,  or  real 
retrograde  varieties,  I  have  found  three,  all  of 
them  in  a  flowering  condition  in  the  field.  I 
have  given  them  the  names  of  laevi folia,  brevi- 
stylis  and  nanella. 


New  Species  of  Oenothera  527 

The  laevifolia,  or  smooth-leaved  variety,  was 
one  of  the  very  first  deviating  types  found  in 
the  original  field.  This  was  in  the  summer  of 
1887,  seventeen  years  ago.  It  formed  a  little 
group  of  plants  growing  at  some  distance  from 
the  main  body,  in  the  same  field.  I  found  some 
rosettes  and  some  flowering  stems  and  sowed 
some  seed  in  the  fall.  The  variety  has  been 
quite  constant  in  the  field,  neither  increasing 
in  number  of  individual  plants  nor  changing 
its  place,  though  now  closely  surrounded  by  oth- 
er Lamarckianas.  In  my  garden  it  has  proved 
to  be  constant  from  seed,  never  reverting  to  the 
original  lamarckiana,  provided  intercrossing 
was  excluded. 

It  is  chiefly  distinguished  from  Lamarck's 
evening-primrose  by  its  smooth  leaves,  as  the 
name  indicates.  The  leaves  of  the  original  form 
show  numerous  sinuosities  in  their  blades,  not 
at  the  edge,  but  anywhere  between  the  veins. 
The  blade  shows  numbers  of  convexities  on 
either  surface,  the  whole  surface  being  undu- 
lated in  this  manner;  it  lacks  also  the  bright- 
ness of  the  ordinary  evening-primrose  or 
Oenothera  biennis. 

These  undulations  are  lacking  or  at  least  very 
rare  on  the  leaves  of  the  new  laevifolia.  Or- 
dinarily they  are  wholly  wanting,  but  at  times 
single  leaves  with  slight  manifestations  of  this 


528  Mutations 

character  may  make  their  appearance.  They 
warn  us  that  the  capacity  for  such  sinuosities 
is  not  wholly  lost,  but  only  lies  dormant  in  the 
new  variety.  It  is  reduced  to  a  latent  state,  ex- 
actly as  are  the  apparently  lost  characters  of 
so  many  ordinary  horticultural  varieties. 

Lacking  the  undulations,  the  laevifolia-lesiYes 
are  smooth  and  bright.  They  are  a  little  nar- 
rower and  more  slender  than  those  of  the  La- 
marckiana.  The  convexities  and  concavities  of 
leaves  are  said  to  be  useful  in  drv  seasons, 
but  during  wet  summers,  such  as  those  of  the 
last  few  years,  they  must  be  considered  as  very 
harmful,  as  they  retain  some  of  the  water  which 
falls  on  the  plants,  prolonging  the  action  of  the 
water  on  the  leaves.  This  is  considered  by  some 
writers  to  be  of  some  utility  after  slight  show- 
ers, but  was  observed  to  be  a  source  of  weak- 
ness during  wet  weather  in  my  garden,  pre- 
venting the  leaves  from  drying.  Whether  the 
laevifolia  would  do  better  under  such  circum- 
stances, remains  to  be  tested. 

The  flowers  of  the  laevifolia  are  also  in  a 
slight  degree  different  from  those  of  LamarcJc- 
iana.  The  yellow  color  is  paler  and  the  petals 
are  smoother.  Later,  in  the  fall,  on  the  weaker 
side  branches  these  differences  increase.  The 
laevifolia  petals  become  smaller  and  are  often 
not  emarginated  at  the  apex,  becoming  ovate 


Neiv  Species  of  Oenothera  529 

instead  of  obcordate.  This  shape  is  often  the 
most  easily  recognized  and  most  striking  mark 
of  the  variety.  In  respect  to  the  reproductive 
organs,  the  fertility  and  abundance  of  good  seed, 
the  laevifolia  is  by  no  means  inferior  or  superior 
to  the  original  species. 

0.  brevistylis,  or  the  short-styled  evening- 
primrose,  is  the  most  curious  of  all  my  new 
forms.  It  has  very  short  styles,  which  bring 
the  stigmas  only  up  to  the  throat  of  the  calyx- 
tube,  instead  of  upwards  of  the  anthers.  The 
stigmas  themselves  are  of  a  different  shape, 
more  flattened  and  not  cylindrical.  The  pollen 
falls  from  the  anthers  abundantly  on  them,  and 
germinates  in  the  ordinary  manner. 

The  ovary  which  in  lamarckiana  and  in 
all  other  new  forms  is  wholly  underneath  the 
calyx-tube,  is  here  only  partially  so.  This 
tube  is  inserted  at  some  distance  under  its 
summit.  The  insertion  divides  the  ovary  into 
two  parts :  an  upper  and  a  lower  one.  The  up- 
per part  is  much  reduced  in  breadth  and  some- 
what attenuated,  simulating  a  prolongation  of 
the  base  of  the  style.  The  lower  part  is  also 
reduced,  but  in  another  manner.  At  the  time 
of  flowering  it  is  like  the  ovary  of  lamarckiana, 
neither  smaller  nor  larger.  But  it  is  reached 
by  only  a  very  few  pollen-tubes,  and  is  there- 
fore  always   incompletely   fertilized.     It    does 


530  Mutations 

not  fall  off  after  the  fading  away  of  the 
flower,  as  unfertilized  ovaries  usually  do; 
neither  does  it  grow  out,  nor  assume  the  upright 
position  of  normal  capsules.  It  is  checked  in  its 
development,  and  at  the  time  of  ripening  it  is 
nearly  of  the  same  length  as  in  the  beginning. 
Many  of  them  contain  no  good  seeds  at  all ;  from 
others  I  have  succeeded  in  saving  only  a  hun- 
dred seeds  from  thousands  of  capsules. 

These  seeds,  if  purely  pollinated,  and  with 
the  exclusion  of  the  visits  of  insects,  reproduce 
the  variety  entirely  and  without  any  reversion 
to  the  lamarckiana  type. 

Correlated  with  the  detailed  structures  is  the 
form  of  the  flower-buds.  They  lack  the  high 
stigma  placed  above  the  anthers,  which  in  the 
lamarckiana,  by  the  vigorous  growth  of  the 
,  style,  extends  the  calyx  and  renders  the  flower- 
bud  thinner  and  more  slender.  Those  of  the 
hrevistylis  are  therefore  broader  and  more 
swollen.  It  is  quite  easy  to  distinguish  the  in- 
dividuals by  this  striking  character  alone,  al- 
though it  differs  from  the  parent  in  other  par- 
ticulars. 

The  leaves  of  the  0.  hrevistylis  are  more 
rounded  at  the  tip,  but  the  difference  is  only  pro- 
nounced at  times,  slightly  in  the  adult  rosettes, 
but  more  clearly  on  the  growing  summits  of  the 
stems  and  branches.  By  this  character,  the  plants 


New  Species  of  Oenothera  531 

may  be  discerned  among  the  others,  some  weeks 
before  the  flowers  begin  to  show  themselves. 

But  the  character  by  which  the  plants  may 
be  most  easily  recognized  from  a  distance  in  the 
field  is  the  failure  of  the  fruits.  They  were 
found  there  nearly  every  year  in  varying,  but 
always  small  numbers. 

Leaving  the  short-styled  primrose,  we  come 
now  to  the  last  of  our  group  of  retrograde  va- 
rieties. This  is  the  0.  nanella,  or  the  dwarf,  and 
is  a  most  attractive  little  plant.  It  is  very  short 
of  stature,  reaching  often  a  height  of  only  20- 
30  cm.,  or  less  than  one-fourth  of  that  of  the  par- 
ent. It  commences  flowering  at  a  height  of  10- 
15  cm.,  while  the  parent-form  often  measures 
nearly  a  meter  at  this  stage  of  its  development. 
Being  so  very  dwarfed  the  large  flowers  are  all 
the  more  striking.  They  are  hardly  inferior 
to  those  of  the  lamarckiana,  and  agree  with 
them  in  structure.  When  they  fade  away 
the  spike  is  rapidly  lengthened,  and  often  be- 
comes much  longer  than  the  lower  or  vegetative 
part  of  the  stem. 

The  dwarfs  are  one  of  the  most  common  mu- 
tations in  my  garden,  and  were  observed  in  the 
native  locality  and  also  grown  from  seeds  saved 
there.  Once  produced  they  are  absolutely  con- 
stant. I  have  tried  manv  thousands  of  seeds 
from  various   dwarf  mutants,   and  never   ob- 


532  Mutations 

served  any  trace  of  reversion  to  the  lamarcJc- 
iana  type.  I  have  also  cultivated  them  in  suc- 
cessive generations  with  the  same  result.  In 
a  former  lecture  we  have  seen  that  contrary  to 
the  general  run  of  horticultural  belief,  varieties 
are  as  constant  as  the  best  species,  if  kept  free 
from  hybrid  admixtures.  This  is  a  general  rule, 
and  the  exceptions,  or  cases  of  atavism  are  ex- 
tremely rare.  In  this  respect  it  is  of  great  inter- 
est to  observe  that  this  constancy  is  not  an  ac- 
quired quality,  but  is  to  be  considered  as  innate, 
because  it  is  already  fully  developed  at  the  very 
moment  when  the  original  mutation  takes  place. 
From  its  first  leaves  to  the  rosette  period, 
and  through  this  to  the  lengthening  of  the  stem, 
the  dwarfs  are  easily  distinguished  from  any 
other  of  their  congeners.  The  most  remarkable 
feature  is  the  shape  of  the  leaves.  They  are 
broader  and  shorter,  and  especially  at  the  base 
they  are  broadened  in  such  a  way  as  to  become 
apparently  sessile.  The  stalk  is  very  brittle, 
and  any  rough  treatment  may  cause  the  leaves 
to  break  off.  The  young  seedlings  are 
recognizable  by  the  shape  of  the  first  two  or 
three  leaves,  and  when  more  of  them  are  pro- 
duced, the  rosettes  become  dense  and  strikingly 
different  from  others.  Later  leaves  are  more 
nearly  like  the  parent-type,  but  the  petioles  re- 
main short.    The  bases  of  the  blades  are  fre- 


New  Species  of  Oenothera  533 

quently  almost  cordate,  the  laminae  themselves 
varying  from  oblong-ovate  to  ovate  in  outline. 

The  stems  are  often  quite  unbranched,  or 
branched  only  at  the  base  of  the  spike.  Strong 
secondary  stems  are  a  striking  attribute  of  the 
lamarchiana  parent,  but  they  are  lacking,  or 
almost  so  in  the  dwarfs.  The  stem  is  straight 
and  short,  and  this,  combined  with  the  large 
crown  of  bright  flowers,  makes  the  dwarfs  emi- 
nently suitable  for  bed  or  border  plants.  Un- 
fortunately they  are  very  sensitive,  especially 
to  wet  weather. 

Oenothera  gigas  and  0.  rubrinervis,  or  the 
giant,  and  the  red-veined  evening-primroses,  are 
the  names  given  to  two  robust  and  stout  spe- 
cies, which  seem  to  be  equal  in  vigor  to  the 
parent-plant,  while  diverging  from  it  in  strik- 
ing characters.  Both  are  true  elementary 
species,  differentiated  from  lamarckiana  in 
nearly  all  their  organs  and  qualities,  but  not 
showing  any  preponderating  character  of  a 
retrograde  nature.  Their  differences  may 
be  compared  with  those  of  the  elementary 
species  of  other  genera,  as  for  instance,  of 
Draba,  or  of  violets,  as  will  be  seen  by  their 
description. 

The  giant  evening-primrose,  though  not  taller 
in  stature  than  0.  lamarclxiana,  deserves 
its  name  because  it  is  so  much  stouter  in  all  re- 


534  Mutations 

spects.  The  stems  are  robust,  often  with  twice 
the  diameter  of  lamarckiana  throughout.  The 
internodes  are  shorter,  and  the  leaves  more 
numerous,  covering  the  stems  with  a  denser 
foliage.  This  shortness  of  the  internodes  ex- 
tends itself  to  the  spike,  and  for  this  reason  the 
flowers  and  fruits  grow  closer  together  than  on 
the  parent-plant.  Hence  the  crown  of  bright 
flowers,  opening  each  evening,  is  more  dense 
and  more  strikingly  brilliant,  so  much  the  more 
so  as  the  individual  flowers  are  markedly  larger 
than  those  of  the  parents.  In  connection  with 
these  characters,  the  flower-buds  are  seen  to  be 
much  stouter  than  those  of  lamarckiana.  The 
fruits  attain  only  half  the  normal  size,  but  are 
broader  and  contain  fewer,  but  larger  seeds. 

The  rubrinervis  is  in  many  respects  a  coun- 
terpart to  the  gigaSj  but  its  stature  is  more 
slender.  The  spikes  and  flowers  are  those  of 
the  lamarckiana,  but  the  bracts  are  narrower. 
Red  veins  and  red  streaks  on  the  fruits  afford 
a  striking  differentiating  mark,  though  they  are 
not  absolutely  lacking  in  the  parent-species. 
A  red  hue  may  be  seen  on  the  calyx,  and  even 
the  yellow  color  of  the  petals  is  somewhat  deep- 
ened in  the  same  way.  Young  plants  are  often 
marked  by  the  pale  red  tinge  of  the  mid-veins, 
but  in  adult  rosettes,  or  from  lack  of  sunshine, 
this  hue  is  often  very  faint. 


'New  Species  of  Oenothera  535 

The  leaves  are  narrow,  and  a  curious  feature 
of  this  species  is  the  great  brittleness  of  the 
leaves  and  stems,  especially  in  annual  individ- 
uals, especially  in  those  that  make  their  stem 
and  flowers  in  the  first  year.  High  turgid- 
ity  and  weak  development  of  the  mechanical 
and  supporting  tissues  are  the  anatomical  cause 
of  this  deficiency,  the  bast-fibers  showing  thin- 
ner walls  than  those  of  the  parent-type  under 
the  microscope.  Young  stems  of  ruhrinervis 
may  be  broken  off  by  a  sharp  stroke,  and 
show  a  smooth  rupture  across  all  the  tissues, 
while  those  of  lamarckiana  are  very  tough  and 
strong. 

Both  the  giant  and  the  red-veined  species  are 
easily  recognized  in  the  rosette-stage.  Even  the 
very  young  seedlings  of  the  latter  are  clearly 
differentiated  from  the  lamarckiana,  but  often 
a  dozen  leaves  are  required,  before  the  dif- 
ference may  be  seen.  Under  such  circumstances 
the  young  plants  must  reach  an  age  of 
about  two  months  before  it  is  possible  to 
discern  their  characters,  or  at  least  before 
these  characters  have  become  reliable  enough 
to  enable  us  to  judge  of  each  individual 
without  doubt.  But  the  divergencies  rapidly 
become  greater.  The  leaves  of  0.  gigas  are 
broader,  of  a  deeper  green,  the  blade  more 
sharply  set  off  against  the  stalk,  all  the  ro- 


536  Mutations 

settes  becoming  stout  and  crowded  with  leaves. 
Those  of  0.  rubrinervis  on  the  contrary  are 
thin,  of  a  paler  green  and  with  a  silvery  white 
surface;  the  blades  are  elliptic,  often  being 
only  2  cm.  or  less  in  width.  They  are  acute 
at  the  apex  and  gradually  narrowed  into  the 
petiole. 

It  is  quite  evident  that  such  pale  narrow 
leaves  must  produce  smaller  quantities  of  or- 
ganic food  than  the  darker  green  and  broad 
organs  of  the  gigas.  Perhaps  this  fact  is  ac- 
countable partly,  at  least,  for  the  more  robust 
growth  of  the  giant  in  the  second  year.  Per- 
haps also  some  relation  exists  between  this  dif- 
ference in  chemical  activity  and  the  tendency 
to  become  annual  or  biennial.  The  gigas,  as  a 
rule,  produces  far  more,  and  the  riihrinervis 
far  less  biennial  plants  than  the  lamarckiana. 
Annual  culture  for  the  one  is  as  unreliable  as 
biennial  culture  for  the  other.  Rubrinervis 
may  be  annual  in  apparently  all  specimens,  in 
sunny  seasons,  but  gigas  will  ordinarily  remain 
in  the  state  of  rosettes  during  the  entire 
first  summer.  It  would  be  very  interesting 
to  obtain  a  fuller  insight  into  the  relation 
of  the  length  of  life  to  other  qualities,  but 
as  yet  the  facts  can  only  be  detailed  as 
they  stand. 

Both  of  these  stout  species  have  been  found 


New  Species  of  Oenothera  537 

quite  constant  from  the  very  first  moment  of 
their  appearance.  I  have  cultivated  them  from 
seed  in  large  numbers,  and  they  have  never  re- 
verted to  the  lamarckiana.  From  this  they 
have  inherited  the  mutability  or  the  capacity  of 
producing  at  their  turn  new  mutants.  But  they 
seem  to  have  done  so  incompletely,  changing  in 
the  direction  of  more  absolute  constancv.  This 
was  especially  observed  in  the  case  of  rubri- 
nervis,  which  is  not  of  such  rare  occurrence  as 
0.  gigas,  and  which  it  has  been  possible  to  study 
in  large  numbers  of  individuals.  So  for  in- 
stance, '^  the  red-veins  ''  have  never  produced 
any  dwarfs,  notwithstanding  they  are  produced 
very  often  by  the  parent-tj^pe.  And  in  crossing- 
experiments  also  the  red- veins  gave  proof  of  the 
absence  of  a  mutative  capacity  for  their  produc- 
tion. 

Leaving  the  robust  novelties,  we  may  now 
take  up  a  couple  of  forms,  which  are  equally 
constant,  and  differentiated  from  the  parent- 
species  in  exactly  the  same  manner,  though  by 
other  characters,  but  which  are  so  obviously 
weak  as  to  have  no  manifest  chance  of  self- 
maintenance  in  the  wild  state.  These  are  the 
whitish  and  the  oblong-leaved  evening-prim- 
roses or  the  Oenothera  alhicla  and  ohlonga. 

Oenothera  albida  is  a  very  weak  species,  with 
whitish,  narrow  leaves,  which  are  evidently  in- 


538  Mutations 

capable  of  producing  sufficient  quantities  of  or- 
ganic food.  The  young  seedling-plants  are  soon 
seen  to  lag  behind,  and  if  no  care  is  taken  of 
them  they  are  overgrown  by  their  neighbors. 
It  is  necessary  to  take  them  out,  to  transplant 
them  into  pots  with  richly  manured  soil,  and 
to  give  them  all  the  care  that  should  be  given 
to  weak  and  sickly  plants.  If  this  is  done  fully 
grown  rosettes  may  be  produced,  which  are 
strong  enough  to  keep  through  the  winter.  In 
this  case  the  individual  leaves  become  stronger 
and  broader,  with  oblong  blades  and  long 
stalks,  but  retain  their  characteristic  whitish 
color. 

In  the  second  year  the  stems  become  relative- 
ly stout.  Not  that  they  become  equal  to  those 
of  lamarckiana,  but  they  become  taller  than 
might  have  been  expected  from  the  weakness  of 
the  plants  in  the  previous  stages.  The  flowers 
and  racemes  are  nearly  as  large  as  those  of  the 
parent-form,  the  fruits  only  a  little  thinner  and 
containing  a  smaller  quantity  of  seed.  From 
these  seeds  I  have  grown  a  second  and  a  third 
generation,  and  observed  that  the  plants  remain 
true  to  their  type. 

0.  ohlonga  may  be  grown  either  as  an  annual, 
or  as  a  biennial.  In  the  first  case  it  is  very 
slender  and  weak,  bearing  only  small  fruits  and 
few  seeds.    In  the  alternative  case  however,  it 


New  Species  of  Oenothera  539 

becomes  densely  branched,  bearing  flowers  on 
quite  a  number  of  racemes  and  yielding  a  full 
harvest  of  seeds.  But  it  always  remains  a  small 
plant,  reaching  about  half  the  height  of  that  of 
lamarckiana. 

When  very  young  it  has  broader  leaves,  but 
in  the  adult  rosettes  the  leaves  become  very  nar- 
row, but  fleshy  and  of  a  bright  green  color. 
They  are  so  crowded  as  to  leave  no  space  be- 
tween them  unoccupied.  The  flowering  spikes 
of  the  second  year  bear  long  leaf-like  bracts 
under  the  first  few  flowers,  but  those  arising 
later  are  much  shorter.  Numerous  little  cap- 
sules cover  the  axis  of  the  spike  after  the  fading 
away  of  the  petals,  constituting  a  very  striking 
differentiating  mark.  This  species  also  was 
found  to  be  quite  constant,  if  grown  from  pure 
seed. 

We  have  now  given  the  descriptions  of  seven 
new  forms,  which  diverge  in  different  ways  from 
the  parent-type.  All  were  absolutely  constant 
from  seed.  Hundreds  or  thousands  of  seedlings 
may  have  arisen,  but  they  always  come  true 
and  never  revert  to  the  original  0.  lamarckiana 
type.  From  this  they  have  inherited  the  condi- 
tion of  mutability,  either  completely  or  partly, 
and  according  to  this  they  may  be  able  to  pro- 
duce new  forms  themselves.  But  this  occurs 
only  rarely,  and  combinations  of  more  than  one 


540  Mutations 

type  in  one  single  plant  seem  to  be  limited  to  the 
admixture  of  the  dwarf  stature  with  the  charac- 
ters of  the  other  new  species. 

These  seven  novelties  do  not  comprise  the 
whole  range  of  the  new  productions  of  my  0. 
lamarckiana.  But  they  are  the  most  interest- 
ing ones.  Others,  as  the  0.  semilata  and  the  0. 
leptocarpa  are  quite  as  constant  and  quite  as 
distinct,  but  have  no  special  claims  for  a  closer 
description.  Others  again  were  sterile,  or  too 
weak  to  reach  the  adult  stage  and  to  yield  seeds, 
and  no  reliable  description  or  appreciation  can 
be  given  on  the  ground  of  the  appearance  of 
a  single  individual. 

Contrasted  with  these  groups  of  constant 
forms  are  three  inconstant  types  which  we  now 
take  up.  They  belong  to  two  different  groups, 
according  to  the  cause  of  their  inconstancy.  In 
one  species  which  I  call  0.  lata,  the  question 
of  stability  or  instability  must  remain  wholly 
unsolved,  as  only  pistillate  flowers  are  produced, 
and  no  seed  can  be  fertilized  save  by  the  use  of 
the  pollen  of  another  form,  and  therefore  by 
hybridization.  The  other  head  comprises  two 
fertile  forms,  0.  scintillans  and  0.  elliptica, 
which  may  easily  be  fertilized  with  their  own 
pollen,  but  which  gave  a  progeny  only  partly 
sunilar  to  the  parents. 

The  Oenothera  lata  is  a  very  distinct  form 


New  Species  of  Oenothera         541 

which  was  found  more  than  once  in  the  field,  and 
recently  (1902)  in  a  luxuriant  flowering  speci- 
men. It  has  likewise  been  raised  from  seeds 
collected  in  different  years  at  the  original  sta- 
tion. It  is  also  wholly  pistillate.  Apparently  the 
anthers  are  robust,  but  they  are  dry,  wrinkled 
and  nearly  devoid  of  contents.  The  inner  wall 
of  cells  around  the  groups  of  pollen  grow  out 
instead  of  being  resorbed,  partly  filling  the 
cavity  which  is  left  free  by  the  miscarriage  of 
the  pollen-grains.  This  miscarriage  does  not 
affect  all  the  grains  in  the  same  degree,  and 
under  the  microscope  a  few  of  them  with  an  ap- 
parently normal  structure  may  be  seen.  But  the 
contents  are  not  normally  developed,  and  I  have 
tried  in  vain  to  obtain  fertilization  with  a  large 
number  of  flowers.  Only  by  cross-fertilization 
does  0.  lata  produce  seeds,  and  then  as  freely  as 
the  other  species  when  self-fertilized.  Of  course 
its  chance  of  ever  founding  a  wild  type  is  pre- 
cluded by  this  defect. 

0.  lata  is  a  low  plant,  with  a  limp  stem,  bent 
tips  and  branches,  all  very  brittle,  but  with 
dense  foliage  and  luxuriant  growth.  It  has 
bright  yellow  flowers  and  thick  flower-buds. 
But  for  an  unknown  reason  the  petals  are  apt  to 
unfold  only  partially  and  to  remain  wrinkled 
throughout  the  flowering  time.  The  stigmas 
are  slightly  divergent  from  the  normal  type, 


542  Mutations 

also  being  partly  united  with  one  another,  and 
laterally  with  the  summit  of  the  style,  but  with- 
out detriment  to  their  function. 

Young  seedlings  of  lata  may  be  recognized  by 
the  very  first  leaves.  They  have  a  nearly  or- 
bicular shape  and  are  very  sharply  set  olf 
against  their  stalk.  The  surface  is  very  un- 
even, with  convexities  and  concavities  on  both 
sides.  This  difference  is  lessened  in  the  later 
leaves,  but  remains  visible  throughout  the  whole 
life  of  the  plant,  even  during  the  flowering  sea- 
son. Broad,  sinuate  leaves  with  rounded  tips 
are  a  sure  mark  of  0.  lata.  On  the  smnmits  of 
the  stems  and  branches  they  are  crowded  so  as 
to  form  rosettes. 

Concerning  inheritance  of  these  characteris- 
tics nothing  can  be  directly  asserted  because  of 
the  lack  of  pollen.  The  new  type  can  only.be 
perpetuated  by  crosses,  either  with  the  parent- 
form  or  some  other  mutant.  I  have  fertilized 
it,  as  a  rule,  with  lamarckiana  pollen,  but  have 
often  also  used  that  from  nanella  and  others.  In 
doing  so,  the  lata  repeats  its  character  in  part  of 
its  offspring.  This  part  seems  to  be  independ- 
ent of  the  nature  of  the  pollen  used,  but  is  very 
variable  according  to  external  circumstances. 
On  the  average  one-fourth  of  the  offspring  be- 
come lata^  the  others  assuming  the  type  of  the 
pollen-parent,   if  this   was   a   lamarckiana    or 


New  Species  of  Oenothera         543 

partly  this  ij^Q  and  partly  that  of  any  other  of 
the  new  species  derived  from  lamarckiana,  that 
might  have  been  used  as  the  pollen-parent.  This 
average  seems  to  be  a  general  rule,  recurring 
in  all  experiments,  and  remaining  unchanged 
through  a  long  series  of  successive  generations. 
The  fluctuations  around  this  mean  go  up  to  near- 
ly 50;^  and  down  nearly  to  1^,  but,  as  in  other 
cases,  such  extreme  deviations  from  the  aver- 
age are  met  with  only  exceptionally. 

The  second  category  includes  the  inconstant 
but  perfectly  fertile  species.  I  have  already 
given  the  names  of  the  only  two  forms,  which 
deserve  to  be  mentioned  here. 

One  of  them  is  called  scintillans  or  the  shiny 
evening-primrose,  because  its  leaves  are  of  a 
deep  green  color  with  smooth  surfaces,  glistening 
in  the  sunshine.  On  the  young  rosettes  these 
leaves  are  somewhat  broader,  and  afterwards 
somewhat  narrower  than  those  of  0.  lamarck- 
iana at  the  corresponding  ages.  The  plants 
themselves  always  remain  small,  never  reaching 
the  stature  of  the  ancestral  type.  They  are 
likewise  much  less  branched.  Thev  can  easilv 
be  cultivated  in  annual  generations,  but  then 
do  not  become  as  fully  developed  and  as  fertile 
as  when  flowering  in  the  second  year.  The 
flowers  have  the  same  structure  as  those  of  the 
lamarckiana,  but  are  of  a  smaller  size. 


544  Mutations 

Fertilizing  the  flowers  artificially  witli  tlieir 
own  pollen,  excluding  the  visiting  insects  by 
means  of  paper  bags,  and  saving  and  sowing 
the  seed  of  each  individual  separately,  fur- 
nishes all  the  requisites  for  the  estimation  of  the 
degree  of  stability  of  this  species.  In  the  first 
few  weeks  the  seed-pans  do  not  show  any  un- 
equality,  and  often  the  young  plants  must  be  re- 
planted at  wider  intervals,  before  anything 
can  be  made  out  with  certainty.  But  as  soon 
as  the  rosettes  begin  to  fill  it  becomes  mani- 
fest that  some  of  them  are  more  backward  than 
others  in  size.  Soon  the  smaller  ones  show 
their  deeper  green  and  broader  leaves,  and 
thereby  display  the  attributes  of  the  scintillans. 
The  other  grow  faster  and  stronger  and  exhibit 
all  the  characteristics  of  ordinary  lamarcki- 
anas. 

The  numerical  proportion  of  these  two  groups 
has  been  found  different  on  different  occasions. 
Some  plants  give  about  one-third  scintillans 
and  two-thirds  lama^^cJciana,  while  the  progeny 
of  individuals  of  another  strain  show  exactly 
the  reverse  proportion. 

Two  points  deserve  to  be  noticed.  First  the 
progeny  of  the  scintillans  appears  to  be  mutable 
in  a  large  degree,  exceeding  even  the  lamarcki- 
ana.  The  same  forms  that  are  produced  most 
often  by  the  parent-family  are  also  most  ordi- 


New  Species  of  Oenothera  545 

narily  met  with  among  the  offspring  of  the 
shiny  evening  -  primrose.  They  are  oblonga, 
lata  and  nanella.  Oblonga  was  observed  at 
times  to  constitute  as  much  as  1%  or  more  of 
the  sowings  of  scintillans,  while  lata  and 
nanella  were  commonly  seen  only  in  a  few 
scattering  individuals,  although  seldom  lacking 
in  experiments  of  a  sufficient  size. 

Secondly  the  instability  seems  to  be  a  con- 
stant quality,  although  the  words  themselves  are 
at  first  sight,  contradictory.  I  mean  to  con- 
vey the  conception  that  the  degree  of  instability 
remains  unchanged  during  successive  genera- 
tions. This  is  a  very  curious  fact,  and  strongly 
reminds  us  of  the  hereditary  conditions  of 
striped-flower  varieties.  But,  on  the  contrary, 
the  atavists,  which  are  here  the  individuals 
with  the  stature  and  the  characteristics  of  the 
lamarckiana,  have  become  lamarckianas  in 
their  hereditary  qualities,  too.  If  their  seed  is 
saved  and  sown,  their  progeny  does  not  contain 
any  scintillans^  or  at  least  no  more  than  might 
arise  by  ordinary  mutations. 

One  other  inconstant  new  species  is  to  be 
noted,  but  as  it  was  very  rare  both  in  the  field 
and  in  my  cultures,  and  as  it  was  difficult  of  cul- 
tivation, little  can  as  yet  be  said  about  it.  It  is 
the  Oenothera  elliptica,  with  narrow  elliptical 
leaves  and  also  with   elliptical  petals.     It  re- 


546  Mutations 

peats  its  type  only  in  a  very  small  proportion 
of  its  seed. 

All  in  all  we  thus  have  a  group  of  a  dozen  new 
types,  springing  from  an  original  form  in  one 
restricted  locality,  and  seen  to  grow  there, 
or  arising  in  the  garden  from  seeds  collected 
from  the  original  locality.  Without  any  doubt 
the  germs  of  the  new  types  are  fully  developed 
within  the  seed,  ready  to  be  evolved  at  the  time 
of  germination.  More  favorable  conditions  in 
the  field  would  no  doubt  allow  all  of  the  de- 
scribed new  species  to  unfold  their  attributes 
there,  and  to  come  into  competition  with  each 
other  and  with  the  common  parents.  But  ob- 
viously this  is  only  of  secondary  importance, 
and  has  no  influence  on  the  fact  that  a  number 
of  new  types,  analogous  to  the  older  swarms  of 
Braha,  Viola  and  of  many  other  poljnnorphous 
species,  have  been  seen  to  arise  directly  in  the 
wild  state. 


Lecture  XIX 

EXPERIMENTAL  PEDIGREE-CULTURES 

The  observation  of  the  production  of  mutants 
in  the  field  at  Hilversum,  and  the  subsequent 
cultivation  of  the  new  types  in  the  garden  at 
Amsterdam,  gives  ample  proof  of  the  mutability 
of  plants.  Furthermore  it  furnishes  an  analogy 
with  the  hypothetical  origin  of  the  swarms  of 
species  of  Draba  and  Viola.  Last  but  not  least 
important  it  affords  material  for  a  complete 
systematic  and  morphologic  study  of  the  new- 
ly arisen  group  of  forms. 

The  physiologic  laws,  however,  which  gov- 
ern this  process  are  only  very  imperfectly  re- 
vealed by  such  a  study.  The  instances  are  too 
few.  Moreover  the  seeds  from  which  the  mu- 
tants spring,  escape  observation.  It  is  simply 
impossible  to  tell  from  which  individual  plants 
they  have  been  derived.  The  laevifoUa  and  the 
brevistylis  have  been  found  almost  every  year, 
the  first  always  recurring  on  the  same  spot,  the 
second  on  various  parts  of  the  original  field.  It 
is   therefore   allowable  to   assume   a   common 

547 


548  Mutations 

origin  for  all  the  observed  individuals  of  either 
strain.  But  whether,  besides  this,  similar 
strains  are  produced  anew  by  the  old  lamarcki- 
ana  group,  it  is  impossible  to  decide  on  the  sole 
ground  of  these  field-observations. 

The  same  holds  good  with  the  other  novelties. 
Even  if  one  of  them  should  germinate  repeated- 
ly, without  ever  opening  its  flowers,  the  possi- 
bility could  not  be  excluded  that  the  seeds  might 
have  come  originally  from  the  same  capsule  but 
lain  dormant  in  the  earth  during  periods  of  un- 
equal length. 

Other  objections  might  be  cited  that  can  only 
be  met  by  direct  and  fully  controlled  experi- 
ments. Next  to  the  native  locality  comes  the  ex- 
perimental garden.  Here  the  rule  prevails  that 
every  plant  must  be  fertilized  with  pollen  of  its 
own,  or  with  pollen  of  other  individuals  of 
known  and  recorded  origin.  The  visits  of  in- 
sects must  be  guarded  against,  and  no  seeds 
should  be  saved  from  flowers  which  have  been 
allowed  to  open  without  this  precaution.  Then 
the  seeds  of  each  individual  must  be  saved  and 
sown  separately,  so  as  to  admit  of  an  apprecia- 
tion, and  if  necessary,  a  numerical  determina- 
tion of  the  nature  of  its  progeny.  And  last  but 
not  least  the  experiments  should  be  conducted 
in  a  similar  manner  during  a  series  of  successive 
years. 


Experimental  Pedigree-Cultures        549 

I  have  made  four  such  experiments,  each  com- 
prising the  handling  of  many  thousands  of  in- 
dividual plants,  and  lasting  through  ^ve  to  nine 
generations.  At  the  beginning  the  plants  were 
biennial,  as  in  the  native  locality,  but  later  I 
learned  to  cultivate  them  in  annual  genera- 
tions. They  have  been  started  from  different 
plants  and  seeds,  introduced  from  the  original 
field  into  my  garden  at  Amsterdam. 

It  seems  sufficient  to  describe  here  one  of 
these  pedigree-cultures,  as  the  results  of  all  four 
were  similar.  In  the  fall  of  1886  I  took  nine 
large  rosettes  from  the  field,  planted  them  to- 
gether on  an  isolated  spot  in  the  garden,  and 
harvested  their  seeds  the  next  year.  These  nine 
original  plants  are  therefore  to  be  considered 
as  constituting  the  first  generation  of  my  race. 
The  second  generation  was  sown  in  1888  and 
flowered  in  1889.  It  at  once  yielded  the  ex- 
pected result.  15000  seedlings  were  tested 
and  examined,  and  among  them  10  showed 
diverging  characters.  They  were  properly 
protected,  and  proved  to  belong  to  two  new 
types.  5  of  them  were  lata  and  5  nanella. 
They  flowered  next  year  and  displayed  all  the 
characters  as  described  in  our  preceding  lec- 
ture. Intermediates  between  them  and  the  gen- 
eral type  were  not  found,  and  no  indication  of 
their  appearance  was  noted  in  their  parents. 


550  Mutations 

They  came  into  existence  at  once,  fully  equipped, 
without  preparation  or  intermediate  steps.  No 
series  of  generations,  no  selection,  no  struggle 
for  existence  was  needed.  It  was  a  sudden  leap 
into  another  type,  a  sport  in  the  best  acceptation 
of  the  word.  It  fulfilled  my  hopes,  and  at  once 
gave  proof  of  the  possibility  of  the  direct  obser- 
vation of  the  origin  of  species,  and  of  the  ex- 
perimental control  thereof. 

The  third  generation  was  in  the  main  a  repeti- 
tion of  the  second.  I  tried  some  10000  seed- 
lings and  found  three  lata  and  three  nanella,  or 
nearly  the  same  proportion  as  in  the  first  in- 
stance. But  besides  these  a  rubrinervis  made 
its  appearance  and  flowered  the  following  year. 
This  fact  at  once  revealed  the  possibility  that  the 
instability  of  lamarckiana  might  not  be  re- 
stricted to  the  three  new  types  now  under  obser- 
vation. Hence  the  question  arose  how  it  would 
be  possible  to  obtain  other  types  or  to  find  them 
if  they  were  present.  It  was  necessary  to 
have  better  methods  of  cultivation  and  examina- 
tion of  the  young  plants.  Accordingly  I  de- 
voted the  three  succeeding  years  to  working  on 
this  problem. 

I  found  that  it  was  not  at  all  necessary  to 
sow  any  larger  quantities  of  seed,  but  that  the 
young  plants  must  have  room  enough  to  develop 
into  full   and  free  rosettes.     Moreover  I  ob- 


Experimental  Pedigree-Cultures       551 

served  that  the  attributes  of  lata  and  nanella, 
which  I  now  studied  in  the  offspring  of  my  first 
mutants,  were  clearly  discernible  in  extreme 
youth,  while  those  of  rubrinervis  remained  con- 
cealed some  weeks  longer.  Hence  I  con- 
cluded that*the  young  plants  should  be  examined 
from  time  to  time  until  they  proved  clearly  to  be 
onlv  normal  lamarckiana.  Individuals  ex- 
hibiting  any  deviation  from  the  type,  or  even 
giving  only  a  slight  indication  of  it,  were  forth- 
with taken  out  of  the  beds  and  planted  separate- 
ly, under  circumstances  as  favorable  as  possible. 
They  were  established  in  pots  with  well-manured 
soil  and  kept  under  glass,  but  fully  exposed  to 
sunshine.  As  a  rule  they  grew  very  fast,  and 
could  be  planted  out  early  in  June.  Some  of 
them,  of  course,  proved  to  have  been  erroneous- 
ly taken  for  mutants,  but  many  exhibited  new 
characters. 

All  in  all  I  had  334  young  plants  which  did 
not  agree  with  the  parental  tjipe.  As  I  exam- 
ined some  14000  seedlings  altogether,  the  result 
was  estimated  at  about  2.5^.  This  proportion 
is  much  larger  than  in  the  yields  of  the  two  first 
generations  and  illustrates  the  value  of  im- 
proved methods.  No  doubt  many  good  muta- 
tions had  been  overlooked  in  the  earlier  observa- 
tions. 

As   was    to   be    expected,   lata   and   nanella 


552  Mutations 

were  repeated  in  this  third  generation  (1895). 
I  was  sure  to  get  nearly  all  of  them,  without  any 
important  exceptions,  as  I  now  knew  how  to  de- 
tect them  at  almost  any  age.  In  fact,  I  found 
many  of  them;  as  many  as  60  nanella  and  73 
lata,  or  nearly  .5^  of  each.  Rubrinervis  also 
recurred,  and  was  seen  in  8  specimens.  It 
was  much  more  rare  than  the  two  first-named 
types. 

But  the  most  curious  fact  in  that  year  was 
the  appearance  of  ohlonga.  No  doubt  I  had 
often  seen  it  in  former  years,  but  had  not  at- 
tached any  value  to  the  very  slight  differences 
from  the  type,  as  they  then  seemed  to  me.  I 
knew  now  that  any  divergence  was  to  be  es- 
teemed as  important,  and  should  be  isolated  for 
further  observation.  This  showed  that  among 
the  selected  specimens  not  less  than  176,  or  more 
than  1%  belonged  to  the  ohlonga  type.  This 
type  was  at  that  time  quite  new  to  me,  and  it  had 
to  be  kept  through  the  winter,  to  obtain  stems 
and  flowers.  It  proved  to  be  as  uniform  as  its 
three  predecessors,  and  especially  as  sharply 
contrasted  with  lamarchiana.  The  opportuni- 
ty for  the  discovery  of  any  intermediates  was  as 
favorable  as  could  be,  because  the  distinguish- 
ing marks  were  hardly  beyond  doubt  at  the  time 
of  the  selection  and  removal  of  the  young  plants. 
But  no  connecting  links  were  found. 


Experimental  Pedigree-Cultures        553 

The  same  holds  good  for  albida,  which  ap- 
peared in  15  specunens,  or  in  O.W,  of  the  whole 
culture.  By  careful  cultivation  these  plants 
proved  not  to  be  sickly,  but  to  belong  to  a  new, 
though  weak  type.  It  was  evident  that  I  had 
already  seen  them  in  former  years,  but  having 
failed  to  recognize  them  had  allowed  them  to  be 
destroyed  at  an  early  age,  not  knowing  how  to 
protect  them  against  adverse  circumstances. 
Even  this  time  I  did  not  succeed  in  getting  them 
strong  enough  to  keep  through  the  winter. 

Besides  these,  two  new  types  were  observed, 
completing  the  range  of  all  that  have  since  been 
recorded  to  regularly  occur  in  this  family. 
They  were  scintillans  and  gig  as.  The  first 
was  obtained  in  the  way  just  described.  The 
other  hardly  escaped  being  destroyed,  not  hav- 
ing showed  itself  early  enough,  and  being  left  in 
the  bed  after  the  end  of  the  selection.  But  as 
it  was  necessary  to  keep  some  rosettes  through 
the  winter  in  order  to  have  biennial  flowering 
plants  to  furnish  seeds,  I  selected  in  August 
about  30  of  the  most  vigorous  plants,  planted 
them  on  another  bed  and  gave  them  sufficient 
room  for  their  stems  and  branches  in  the  follow- 
ing summer.  Most  of  tliem  sent  up  robust 
shoots,  but  no  difference  was  noted  till  the  first 
flowers  opened.  One  plant  had  a  much  larger 
crown  of  bright  blossoms  than  any  of  the  others. 


554  Mutations 

As  soon  as  these  flowers  faded  away,  and  the 
young  fruits  grew  out,  it  became  clear  that  a 
new  type  was  showing  itself.  On  that  indica- 
tion I  removed  all  the  already  fertilized  flowers 
and  young  fruits,  and  protected  the  buds  from 
the  visits  of  insects.  Thus  the  isolated  flowers 
were  fertilized  with  their  own  pollen  only,  and 
I  could  rely  ujDon  the  purity  of  the  seed  saved. 
This  lot  of  seeds  was  sown  in  the  spring  of  1897 
and  yielded  a  uniform  crop  of  nearly  300  young 
gigas  plants. 

Having  found  how  much  depends  upon  the 
treatment,  I  could  gradually  decrease  the  size  of 
my  cultures.  Evidently  the  chance  of  discover- 
ing new  types  would  be  lessened  thereby,  but  the 
question  as  to  the  repeated  production  of  the 
same  new  forms  could  more  easily  and  more 
clearly  be  answered  in  this  way.  In  the  follow- 
ing year  (1896)  I  sowed  half  as  many  seeds  as 
formerly,  and  the  result  proved  quite  the  same. 
With  the  exception  of  gigas  all  the  described 
forms  sprang  anew  from  the  purely  fertilized 
ancestry  of  normal  Lamarckianas.  It  was  now 
the  fifth  generation  of  my  pedigree,  and  thus  I 
was  absolutely  sure  that  the  descendants  of  the 
mutants  of  this  year  had  been  pure  and  without 
deviation  for  at  least  four  successive  genera- 
tions. 

Owing  partly  to  improved  methods  of  selec- 


Experimental  Pedigree-Cultures        555 

tion,  partly  no  doubt  to  chance,  even  more  mu- 
tants were  found  this  year  than  in  the  former. 
Out  of  some  8000  seedlings  I  counted  377  deviat- 
ing ones,  or  nearly  5^,  which  is  a  high  propor- 
tion. Most  of  them  were  ohlonga  and  lata^  the 
same  types  that  had  constituted  the  majority  in 
the  former  year. 

Alhida,  nanella  and  ruhrinervis  appeared  in 
large  numbers,  and  even  scintillanSj  of  which 
I  had  but  a  single  plant  in  the  previous  genera- 
tion, was  repeated  sixfold. 

New  forms  did  not  arise,  and  the  capacity  of 
my  strain  seemed  exhausted.  This  conclusion 
was  strengthened  by  the  results  of  the  next 
three  generations,  which  were  made  on  a  much 
smaller  scale  and  yielded  the  same,  or  at  least 
the  mutants  most  commonly  seen  in  previous 
years. 

Instead  of  giving  the  fignires  for  these  last 
two  years  separately,  I  will  now  summarize  my 
whole  experiment  in  the  form  of  a  pedigree.  In 
this  the  normal  lamarckiana  was  the  main  line, 
and  seeds  were  only  sown  from  plants  after  suf- 
ficient isolation  either  of  the  plants  themselves, 
or  in  the  latter  years  by  means  of  paper  bags 
enclosing  the  inflorescences.  I  have  given  the 
number  of  seedlings  of  lamarckiana  which  were 
examined  each  year  in  the  table  below.  Of 
course  by  far  the  largest  number  of  them  were 


556  Mutations 

thrown  away  as  soon  as  they  showed  their  dif- 
ferentiating characters  in  order  to  make  room 
for  the  remaining  ones.  At  last  only  a  few 
plants  were  left  to  blossom  in  order  to  perpet- 
uate the  race.  I  have  indicated  for  each  genera- 
tion the  number  of  mutants  of  each  of  the  ob- 
served forms,  placing  them  in  vertical  columns 
underneath  their  respective  heads.  The  three 
first  generations  were  biennial,  but  the  five  last 
annual. 


PEDIGREE  OF  A  MUTATING  FAMILY  OF  OENOTHERA  LAMARCKIANA 
IN  THE  EXPERIMENTAL  GARDEN   AT   AMSTERDAM. 


Gener: 

O.gig. 

albida 

obi. 

rubrin. 

Lam. 

nanella 

lata. 

scint, 

VIII. 

5 

1 

0 

1700 

21 

1 

VII. 

9 

0 

3000 

11 

VI. 

11 

29 

3 

1800 

9 

5 

1 

V. 

25 

135 

20 

8000 

49 

142 

6 

IV. 

1 

15 

176 

8 

14000 

60 

73 

1 

III. 

1 

10000 

3 

3 

II. 

15000 

5 

5 

I. 

9 

It  is  most  striking  that  the  various  mutations 
of  the  evening-primrose  display  a  great  degree 
of  regularity.  There  is  no  chaos  of  forms,  no 
indefinite  varying  in  all  degrees  and  in  all  direc- 
tions. Quite  on  the  contrary,  it  is  at  once  evi- 
dent that  very  simple  rules  govern  the  whole 
phenomenon. 

I  shall  now  attempt  to  deduce  these  laws  from 


Experimental  Pedigree-Cultures        557 

my  experiment.  Obviously  they  apply  not  only 
to  our  evening-primroses,  but  may  be  expected 
to  be  of  general  validity.  This  is  at  once 
manifest,  if  we  compare  the  group  of  new  mu- 
tants with  the  swarms  of  elementary  forms 
which  compose  some  of  the  youngest  systematic 
species,  and  which,  as  we  have  seen  before,  are 
to  be  considered  as  the  results  of  previous  mu- 
tations. The  difference  lies  in  the  fact  that  the 
evening-primroses  have  been  seen  to  spring 
from  their  ancestors  and  that  the  drabas 
have  not.  Hence  the  conclusion  that  in  com- 
paring the  two  we  must  leave  out  the  pedigree  of 
the  evening-primroses  and  consider  only  the 
group  of  forms  as  they  finally  show  themselves. 
If  in  doing  so  we  find  sufficient  similarity,  we  are 
justified  in  the  conclusion  that  the  drabas  and 
others  have  probably  originated  in  the  same  way 
as  the  evening-primroses.  Minor  points  of 
course  will  differ,  but  the  main  lines  cannot  have 
complied  with  wholly  different  laws.  All  so- 
called  swarms  of  elementary  species  obviously 
pertain  to  a  single  type,  and  this  type  includes 
our  evening-primroses  as  the  only  controlled 
case. 

Formulating  the  laws  of  mutability  for  the 
evening-primroses  we  therefore  assume  that 
they  hold  good  for  numerous  other  correspond- 
ing cases. 


558  Mutations 

I.  The  first  law  is,  that  new  elementary  spe- 
cies appear  suddenly,  without  intermediate 
steps. 

This  is  a  striking  point,  and  the  one  that  is  in 
the  most  immediate  contradiction  to  current 
scientific  belief.  The  ordinary  conception  as- 
sumes very  slow  changes,  in  fact  so  slow  that 
centuries  are  supposed  to  be  required  to  make 
the  differences  appreciable.  If  this  were  true, 
all  chance  of  ever  seeing  a  new  species  arise 
would  be  hopelessly  small.  Fortunately  the 
evening-primroses  exhibit  contrary  tendencies. 
One  of  the  great  points  of  pedigree-culture  is  the 
fact  that  the  ancestors  of  every  mutant  have 
been  controlled  and  recorded.  Those  of  the  last 
year  have  seven  generations  of  known  lamarck- 
iana  parents  preceding  them.  If  there  had  been 
any  visible  preparation  towards  the  coming  mu- 
tation, it  could  not  have  escaped  observation. 
Moreover,  if  visible  preparation  were  the  rule, 
it  could  hardly  go  on  at  the  same  time  and  in  the 
same  individuals  in  five  or  six  diverging  direc- 
tions, producing  from  one  parent,  gigas  and  na- 
nella,  lata  and  rubrinervis,  ohlonga  and  albida 
and  even  scintillans. 

On  the  other  hand  the  mutants,  that  constitute 
the  first  representatives  of  their  race,  exhibit 
all  the  attributes  of  the  new  type  in  full  display 
at  once.    No  series  of  generations,  no  selection, 


Experimental  Pedigree-Cultures       559 

no  struggle  for  existence  are  needed  to  reach 
this  end.  In  previous  lectures  I  have  mentioned 
that  I  have  saved  the  seeds  of  the  mutants 
whenever  possible,  and  have  always  obtained 
repetitions  of  the  prototype  only.  Reversions 
are  as  absolutely  lacking  as  is  also  a  further  de- 
velopment of  the  new  type.  Even  in  the  case  of 
the  inconstant  f  oinns,  where  part  of  the  progeny 
yearly  return  to  the  stature  of  lamarckiana,  in- 
termediates are  not  found.  So  it  is  also  with 
lata,  which  is  pistillate  and  can  only  be  prop- 
agated by  cross-fertilization.  But  though  the 
current  belief  would  expect  intermediates  at 
least  in  this  case,  thev  do  not  occur.  I  made  a 
pedigree-culture  of  lata  during  eight  successive 
generations,  pollinating  them  in  different  ways, 
and  always  obtained  cultures  which  were  partly 
constituted  of  lata  and  partly  of  lamarckiana 
specimens.  But  the  latas  remained  lata  in  all 
the  various  and  most  noticeable  characters, 
never  showing  any  tendency  to  gradually  revert 
into  the  original  form. 

Intermediate  forms,  if  not  occurring  in  the 
direct  line  from  one  species  to  another,  might  be 
expected  to  appear  perhaps  on  lateral  branches. 
In  this  case  the  mutants  of  one  type,  appearing 
in  the  same  year,  would  not  be  a  pure  type,  but 
would  exhibit  different  degrees  of  deviation 
from  the  parent.     The  best  would  then  have  to 


560  Mutations 

be  chosen  in  order  to  get  the  new  type  in  its  pure 
condition.  Nothing  of  the  kind,  however,  was 
observed.  All  the  oblong a-m\xtsints  were  pure 
oblongas.  The  pedigree  shows  hundreds  of 
them  in  the  succeeding  years,  but  no  difference 
was  seen  and  no  material  for  selection  was  af- 
forded. All  were  as  nearly  equal  as  the  in- 
dividuals of  old  elementary  species. 

II.  New  fonns  spring  laterally  from  the 
main  stem. 

The  current  conception  concerning  the  origin 
of  species  assumes  that  species  are  slowly  con- 
verted into  others.  The  conversion  is  assumed 
to  affect  all  the  individuals  in  the  same  direction 
and  in  the  same  degree.  The  whole  group 
changes  its  character,  acquiring  new  attributes. 
By  inter-crossing  they  maintain  a  common  line 
of  progress,  one  individual  never  being  able  to 
proceed  much  ahead  of  the  others. 

The  birth  of  the  new  species  necessarily 
seemed  to  involve  the  death  of  the  old  one.  This 
last  conclusion,  however,  is  hard  to  understand. 
It  may  be  justifiable  to  assume  that  all  the  in- 
dividuals of  one  locality  are  ordinarily  inter- 
crossed, and  are  moreover  subjected  to  the  same 
external  conditions.  They  might  be  supposed 
to  vary  in  the  same  direction  if  these  conditions 
were  changed  slowly.  But  this  could  of  course 
have  no  possible  influence  on  the  plants  of  the 


Experimental  Pedigree-Cultures        561 

same  species  growing  in  distant  localities,  and 
it  would  be  improbable  they  should  be  affected 
in  the  same  way.  Hence  we  should  conclude 
that  when  a  species  is  converted  into  a  new  type 
in  one  locality  this  is  only  to  be  considered  as 
one  of  numerous  possible  ones,  and  its  alteration 
would  not  in  the  least  change  the  aspect  of  the 
remainder  of  the  species. 

But  even  with  this  restriction  the  general  be- 
lief is  not  supported  by  the  evidence  of  the  even- 
ing-primroses. There  is  neither  a  slow  nor  a 
sudden  change  of  all  the  individuals.  On  the 
contrary,  the  vast  majority  remain  unchanged; 
thousands  are  seen  exactly  repeating  the  orig- 
inal prototype  yearly,  both  in  the  native  field 
and  in  my  garden.  There  is  no  danger  that 
lamarckiana  might  die  out  from  the  act  of  mu- 
tating, nor  that  the  mutating  strain  itself  would 
be  exposed  to  ultimate  destruction  from  this 
cause. 

In  older  swarms,  such  as  Draha  or  Helianthe- 
mum,  no  such  center,  around  which  the  various 
forms  are  grouped,  is  known.  Are  we  to  con- 
clude therefore  that  the  main  strain  has  died 
out?  Or  is  it  perhaps  concealed  among  the 
throng,  being  distinguished  by  no  peculiar  char- 
acter 1  If  our  gig  as  and  rubrinervis  were  grow- 
ing in  equal  numbers  with  the  lamarckiana  in 
the  native  field,  would  it  be  possible  to  decide 


562  Mutations 

which  of  them  was  the  progenitor  of  the  others? 
Of  course  this  could  be  done  by  long  and  tedious 
crossing-experiments,  showing  atavism  in  the 
progeny,  and  thereby  indicating  the  common 
ancestor.  But  even  this  capacity  seems  to  be 
doubtful  and  connected  only  with  the  state  of 
mutability  and  to  be  lost  afterwards.  Therefore 
if  this  period  of  mutation  were  ended,  probably 
there  would  be  no  way  to  decide  concerning  the 
mutual  relationship  of  the  single  species. 

Hence  the  lack  of  a  recognizable  main  stem  in 
swarms  of  elementary  species  makes  it  impossi- 
ble to  answer  the  question  concerning  their  com- 
mon origin. 

Another  phase  of  the  ojDposition  between  the 
prevailing  view  and  my  own  results  seems  far 
more  important.  According  to  the  current  be- 
lief the  conversion  of  a  group  of  plants  growing 
in  any  locality  and  flowering  simultaneously 
would  be  restricted  to  one  type.  In  my  own  ex- 
periments several  new  species  arose  from  the 
parental  form  at  once,  giving  a  wide  range  of 
new  forms  at  the  same  time  and  under  the  same 
conditions. 

III.  Neiv  elementary  species  attain  their  full 
constancy  at  once. 

Constancy  is  not  the  result  of  selection  or  of 
improvement.  It  is  a  quality  of  its  own.  It  can 
neither  be  constrained  bv  selection  if  it  is  absent 


Experimental  Pedigree-Cultures        563 

from  the  beginning,  nor  does  it  need  any  natural 
or  artificial  aid  if  it  is  present.  -  Most  of  my 
new  species  have  proved  constant  from  the  first. 
Whenever  possible,  the  original  mutants  have 
been  isolated  during  the  flowering  period  and 
artificially  self-fertilized.  Such  plants  have  al- 
ways given  a  uniform  progeny,  all  children  ex- 
hibiting the  type  of  the  parent.  No  atavism 
was  observed  and  therefore  no  selection  was 
needed  or  even  practicable. 

Briefly  considering  the  different  forms,  we 
may  state  that  the  full  experimental  proof  has 
been  given  for  the  origin  of  gig  as  and  rubriner- 
visj  for  alhida  and  oblong  a,  and  even  for  na- 
nella,  which  is  to  be  considered  as  of  a  varietal 
nature ;  with  lata  the  decisive  experiment  is  ex- 
cluded by  its  unisexuality.  Laevifolia  and 
brevistylis  were  found  originally  in  the  field, 
and  never  appeared  in  my  cultures.  No  obser- 
vations were  made  as  to  their  origin,  and  seeds 
have  only  been  sown  from  later  generations. 
But  these  have  yielded  uniform  crops,  thereby 
showing  that  there  is  no  ground  for  the  assump- 
tion that  these  two  older  varieties  might  behave 
otherwise  than  the  more  recent  derivatives. 

Scintillans  and  elliptica  constitute  exceptions 
to  the  rule  given.  They  repeat  their  character, 
from  pure  seed,  only  in  part  of  the  offspring.  I 
have  tried  to  deliver  the  scintillans  from  this 


564  Mutations 

incompleteness  of  heredity,  but  in  vain.  The 
succeeding  generations,  if  produced  from  true 
representatives  of  the  new  type,  and  with  pure 
fertilization,  have  repeated  the  splitting  in  the 
same  numerical  proportions.  The  instability 
seems  to  be  here  as  permanent  a  quality  as  the 
stability  in  other  instances.  Even  here  no  se- 
lection has  been  adequate  to  change  the  original 
form. 

IV.  So7ne  of  the  new  strains  are  evidently  ele- 
mentary species,  ivhile  others  are  to  he  consid- 
ered as  retrograde  varieties. 

It  is  often  difficult  to  decide  whether  a  given 
form  belongs  to  one  or  another  of  these  two 
groups.  I  have  tried  to  show  that  the  best 
and  strictest  conception  of  varieties  limits 
them  to  those  forms  that  have  probably 
originated  by  retrograde  or  degressive  steps. 
Elementary  species  are  assumed  to  have  been 
produced  in  a  progressive  way,  adding  one 
new  element  to  the  store.  Varieties  differ  from 
their  species  clearly  in  one  point,  and  this  is 
either  a  distinct  loss,  or  the  assumption  of  a 
character,  which  may  be  met  with  in  other 
species  and  genera.  Laevifolia  is  distin- 
guished by  the  loss  of  the  crinkling  of  the 
leaves,  hrevistylis  by  the  partial  loss  of  the 
epigj-nous  qualities  of  the  flowers,  and  nanella  is 
a  dwarf.     These  three  new  forms  are  therefore 


Experimental  Pedigree-Cultures        565 

considered  to  constitute  only  retrograde  steps, 
and  no  advance.  This  conclusion  has  been  fully 
justified  by  some  crossing  experiments  with 
brevistylis,  which  wholly  complies  with  Men- 
del's law,  and  in  one  instance  with  nanella, 
which  behaves  in  the  same  manner,  if  crossed 
with  ruhrinervis. 

On  the  other  hand,  gigas  and  ruhrinervis,  oh- 
longa  and  alhida  obviously  bear  the  characters 
of  progressive  elementary  species.  They  are 
not  differentiated  from  lamarchiana  by  one  or 
two  main  features.  They  diverge  from  it  in 
nearly  all  organs,  and  in  all  in  a  definite  though 
small  degree.  They  may  be  recognized  as  soon 
as  they  have  developed  their  first  leaves  and  re- 
main discernible  throughout  life.  Their  char- 
acters refer  chiefly  to  the  foliage,  but  no  less  to 
the  stature,  and  even  the  seeds  have  peculiari- 
ties. There  can  be  little  doubt  but  that  all  the 
attributes  of  every  new  species  are  derived  from 
one  principal  change.  But  why  this  should  af- 
fect the  foliage  in  one  manner,  the  flowers  in 
another  and  the  fruits  in  a  third  direction,  re- 
mains obscure.  To  gain  ever  so  little  an  insight 
into  the  nature  of  these  changes,  we  may  best 
compare  the  differences  of  our  evening-prim- 
roses with  those  between  the  two  hundred  ele- 
mentary species  of  Draba  and  other  similar 
instances.    In  doing  so  we  find  the  same  main 


566  Mutations 

feature,  the  minute  differences  in  nearly  all 
points. 

V.  The  ^ame  new  species  are  produced  in  a 
large  number  of  individuals. 

This  is  a  very  curious  fact.  It  embraces  two 
minor  points,  viz :  the  multitude  of  similar  mu- 
tants in  the  same  year,  and  the  repetition  there- 
of in  succeeding  generations.  Obviously  there 
must  be  some  common  cause.  This  cause  must 
be  assumed  to  lie  dormant  in  the  Lamarckianas 
of  my  strain,  and  probably  in  all  of  them,  as  no 
single  parent-plant  proved  ever  to  be  wholly 
destitute  of  mutability.  Furthermore  the  dif- 
ferent causes  for  the  sundry  mutations  must  lie 
latent  together  in  the  same  parent-plant.  They 
obey  the  same  general  laws,  become  active  under 
similar  conditions,  some  of  them  being  more 
easily  awakened  than  others.  The  germs  of  the 
ohlonga,  lata  and  nanella  are  especially  ir- 
ritable, and  are  ready  to  spring  into  activity  at 
the  least  summons,  while  those  of  gig  as  ^  ruhri- 
nervis  and  scintillans  are  far  more  difficult  to 
arouse. 

These  germs  must  be  assumed  to  lie  dormant 
during  many  successive  generations.  This  is 
especially  evident  in  the  case  of  lata  and  nanella, 
which  appeared  in  the  first  year  of  the  pedigree- 
culture  and  which  since  have  been  repeated 
yearly,  and  have  been  seen  to  arise  by  mutation 


Experimental  Pedigree-Cultures        567 

also  during  the  last  season  (1903).  Only  gigas 
appeared  but  once,  but  then  there  is  every  rea- 
son to  assume  that  in  larger  sowings  or  by  a  pro- 
longation of  the  experiments  it  might  have  made 
a  second  appearance. 

Is  the  number  of  such  germs  to  be  supposed 
to  be  limited  or  unlimited?  My  experiment  has 
produced  about  a  dozen  new  forms.  Without 
doubt  I  could  easily  have  succeeded  in  getting 
more,  if  I  had  had  any  definite  reason  to  search 
for  them.  But  such  figures  are  far  from  favor- 
ing the  assumption  of  indefinite  mutability. 
The  group  of  possible  new  forms  is  no  doubt 
sharply  circumscribed.  Partly  so  by  the  mor- 
phologic peculiarities  of  lamarckiana,  which 
seem  to  exclude  red  flowers,  composite  leaves, 
etc.  No  doubt  there  are  more  direct  rea- 
sons for  these  limits,  some  changes  having  taken 
place  initially  and  others  later,  while  the  present 
mutations  are  only  repetitions  of  previous  ones, 
and  do  not  contribute  new  lines  of  development 
to  those  already  existing.  This  leads  us  to  the 
supposition  of  some  common  original  cause, 
which  produced  a  number  of  changes,  but  which 
itself  is  no  longer  at  work,  but  has  left  the  af- 
fected qualities,  and  only  these,  in  the  state  of 
mutability. 

In  nature,  repeated  mutations  must  be  of  far 
greater  significance  than  isolated  ones.     How 


568  Mutations 

great  is  the  chance  for  a  single  individual  to  be 
destroyed  in  the  struggle  for  life!  Hundreds 
of  thousands  of  seeds  are  produced  by  la- 
marckiana  annually  in  the  field,  and  only 
some  slow  increase  of  the  number  of  specimens 
can  be  observed.  Many  seeds  do  not  find  the 
proper  circumstances  for  germination,  or  the 
young  seedlings  are  destroyed  by  lack  of  water, 
of  air,  or  of  space.  Thousands  of  them  are  so 
crowded  when  becoming  rosettes  that  only  a  few 
succeed  in  producing  stems.  Any  weakness 
would  have  destroyed  them.  As  a  matter  of 
fact  they  are  much  oftener  produced  in  the  seed 
than  seen  in  the  field  with  the  usual  unfavorable 
conditions ;  the  careful  sowing  of  collected  seeds 
has  given  proof  of  this  fact  many  times. 

The  experimental  proof  of  this  frequency  in 
the  origin  of  new  types,'Seems  to  overcome  many 
difficulties  offered  by  the  current  theories  on  the 
probable  origin  of  species  at  large. 

VI.  The  relation  hetiveen  mutability  and  fluc- 
tuating variability  has  always  been  one  of  the 
chief  difficulties  of  the  followers  of  Darwin.  The 
majority  assumed  that  species  arise  by  the  slow 
accumulation  of  slight  fluctuating  deviations, 
and  the  mutations  were  only  to  be  considered  as 
extreme  fluctuations,  obtained,  in  the  main,  by  a 
continuous  selection  of  small  differences  in  a 
constant  direction. 


Experimental  Pedigree-Cultures        569 

My  cultures  show  that  quite  the  opposite  is 
to  be  regarded  as  fact.  All  organs  and  all  quali- 
ties of  lamarckiana  fluctuate  and  vary  in  a 
more  or  less  evident  manner,  and  those  which  I 
had  the  opportunity  of  examining  more  closely 
were  found  to  comply  with  the  general  laws  of 
fluctuation.  But  such  oscillating  changes  have 
nothing  in  common  with  the  mutations.  Their 
essential  character  is  the  heaping  up  of  slight 
deviations  around  a  mean,  and  the  occurrence  of 
continuous  lines  of  increasing  deviations,  link- 
ing the  extremes  with  this  group.  Nothing  of 
the  kind  is  observed  in  the  case  of  mutations. 
There  is  no  mean  for  them  to  be  grouped  around 
and  the  extreme  only  is  to  be  seen,  and  it  is 
wholly  unconnected  with  the  original  type.  It 
might  be  supposed  that  on  closer  inspection  each 
mutation  might  be  brought  into  connection  with 
some  feature  of  the  fluctuating  variability.  But 
this  is  not  the  case.  The  dwarfs  are  not  at  all 
the  extreme  variants  of  structure,  as  the  fluctua- 
tion of  the  height  of  the  lamarckiGna  never  de- 
creases or  even  approaches  that  of  the  dwarfs. 
There  is  always  a  gap.  The  smallest  specimens 
of  the  tall  type  are  commonly  the  weakest,  ac- 
cording to  the  general  rule  of  the  relationship 
between  nourishment  and  variation,  but  the 
tallest  dwarfs  are  of  course  the  most  robust 
specimens  of  their  group. 


570  Mutations 

Fluctuating  variability,  as  a  rule,  is  subject  to 
reversion.  The  seeds  of  the  extremes  do  not 
produce  an  offspring  which  fluctuates  around 
their  parents  as  a  center,  but  around  some  point 
on  the  line  which  combines  their  attributes  with 
the  corresponding  characteristic  of  their  ances- 
tors, as  Vilmorin  has  put  it.  No  reversion  ac- 
companies mutation,  and  this  fact  is  perhaps  the 
completest  contrast  in  which  these  two  great 
types  of  variability  are  opposed  to  each  other. 

The  offspring  of  my  mutants  are,  of  course, 
subject  to  the  general  laws  of  fluctuating  varia- 
bility. They  vary,  however,  around  their  own 
mean,  and  this  mean  is  simply  the  type  of  the 
new  elementary  species. 

VII.  The  mutations  take  place  in  nearly  all 
directions. 

Many  authors  assume  that  the  origin  of  spe- 
cies is  directed  by  unknown  causes.  These 
causes  are  assumed  to  work  in  each  single  case 
for  the  improvement  of  the  animals  and  plants, 
changing  them  in  a  manner  corresponding 
in  a  useful  way  to  the  changes  that  take 
place  in  their  environment.  It  is  not  easy  to 
imagine  the  nature  of  these  influences  nor  how 
they  would  bring  about  the  desired  effect. 

This  difficulty  was  strongly  felt  by  Darwin, 
and  one  of  the  chief  purposes  of  his  selection- 
theory    may   be    said    to    have   been    the    at- 


Experiniental  Pedigree-Cultures        571 

tempt  to  surmount  it.  Darwin  tried  to  re- 
place the  unknown  cause  by  natural  agencies, 
which  lie  under  our  immediate  observation. 
On  this  point  Darwin  was  superior  to  his 
predecessors,  and  it  is  chiefly  due  to  the  clear 
conception  of  this  point  that  his  theory  has 
gained  its  deserved  general  acceptance.  Accord- 
ing to  Darwin,  changes  occur  in  all  directions, 
quite  independently  of  the  prevailing  circum- 
stances. Some  may  be  favorable,  others  detri- 
mental, many  of  them  without  significance, 
neither  useful  nor  injurious.  Some  of  them 
will  sooner  or  later  be  destroyed,  while  others 
will  survive,  but  which  of  them  will  survive, 
is  obviously  dependent  upon  whether  their 
particular  changes  agree  with  the  existing 
environic  conditions  or  not.  This  is  what 
Darwin  has  called  the  struggle  for  life. 
It  is  a  large  sieve,  and  it  only  acts  as 
such.  Some  fall  through  and  are  annihilated, 
others  remain  above  and  are  selected,  as  the 
phrase  goes.  Many  are  selected,  but  more  are 
destroyed ;  daily  observation  does  not  leave  any 
doubt  upon  this  point. 

How  the  differences  originate  is  quite  another 
question.  It  has  nothing  to  do  with  the  theory 
of  natural  selection  nor  with  the  struggle  for 
life.  These  have  an  active  part  only  in  the  ac- 
cumulation of  useful  qualities,  and  only  in  so 


572  Mutations 

far  as  they  protect  the  bearers  of  such  charac- 
ters against  being  crowded  out  by  their  more 
poorly  constituted  competitors. 

However,  the  differentiating  characteristics 
of  elementary  species  are  only  very  small.  How 
widely  distant  they  are  from  the  beautiful  adap- 
tative  organizations  of  orchids,  of  insectivorous 
plants  and  of  so  many  others !  Here  the  differ- 
ence lies  in  the  accumulation  of  numerous  ele- 
mentary characters,  which  all  contribute  to  the 
same  end.  Chance  must  have  produced  them, 
and  this  would  seem  absolutely  improbable,  even 
impossible,  were  it  not  for  Darwin's  ingenious 
theory.  Chance  there  is,  but  no  more  than  any- 
where else.  It  is  not  by  mere  chance  that  the 
variations  move  in  the  required  direction.  They 
do  go,  according  to  Darwin's  view,  in  all  direc- 
tions, or  at  least  in  many.  If  these  include  the 
useful  ones,  and  if  this  is  repeated  a  number  of 
times,  cumulation  is  possible;  if  not,  there  is 
simply  no  progression,  and  the  type  remains 
stable  through  the  ages.  Natural  selection  is 
continually  acting  as  a  sieve,  throwing  out  the 
useless  changes  and  retaining  the  real  improve- 
ments. Hence  the  accumulation  in  apparent- 
ly predisposed  directions,  and  hence  the 
increasing  adaptations  to  the  more  specialized 
conditions  of  life.  It  must  be  obvious  to  any 
one  who  can  free  himself  from  the  current  ideas. 


Experimental  Pedigree-Cultures        573 

that  this  theory  of  natural  selection  leaves  the 
question  as  to  how  the  changes  themselves  are 
brought  about,  quite  undecided.  There  are  two 
possibilities,  and  both  have  been  propounded  by 
Darwin.  One  is  the  accumulation  of  the  slight 
deviations  of  fluctuating  variability,  the  other 
consists  of  successive  sports  or  leaps  taking 
place  in  the  same  direction. 

In  further  lectures  a  critical  comparison  of 
the  two  views  will  be  given.  To-day  I  have  only 
to  show  that  the  mutations  of  the  evening-prim- 
roses, though  sudden,  comply  with  the  demands 
made  by  Darwin  as  to  the  form  of  variability 
which  is  to  be  accepted  as  the  cause  of  evolution 
and  as  the  origin  of  species. 

Some  of  my  new  types  are  stouter  and  others 
weaker  than  their  parents,  as  shown  by  gigas 
and  alhida.  Some  have  broader  leaves  and 
some  narrower,  lata  and  ohlonga.  Some  have 
larger  flowers  {gigas)  or  deeper  yellow  ones 
(ruhrinervis)  J  or  smaller  blossoms  (scintillans) y 
or  of  a  paler  hue  (alhida).  In  some  the  cap- 
sules are  longer  (nihrinervis),  or  thicker 
(gigas),  or  more  rounded  (lata),  or  small  (ob- 
longa),  and  nearly  destitute  of  seeds  (brevi- 
stylis).  The  unevenness  of  the  surface  of  the 
leaves  may  increase  as  in  lata^  or  decrease  as  in 
laevifolia.  The  tendency  to  become  annual  pre- 
vails in  riibrinervis,  but  gigas  tends  to  become 


574  Mutations 

biennial.  Some  are  rich  in  pollen,  while  scin- 
tillans  is  poor.  Some  have  large  seeds,  others 
small.  Lata  has  become  pistillate,  while 
brevistylis  has  nearly  lost  the  faculty  to  pro- 
duce seeds.  Some  undescribed  forms  were 
quite  sterile,  and  some  I  observed  which  pro- 
duced no  flowers  at  all.  From  this  statement  it 
may  be  seen  that  nearly  all  qualities  vary  in  op- 
posite directions  and  that  our  group  of  mutants 
affords  wide  material  for  the  sifting  process  of 
natural  selection.  On  the  original  field  the 
laevi folia  and  brevistylis  have  held  their  own 
during  sixteen  years  and  probably  more,  with- 
out, however,  being  able  to  increase  their  num- 
bers to  any  noticeable  extent.  Others  perish 
as  soon  as  they  make  their  appearance,  or  a 
few  individuals  are  allowed  to  bloom,  but  prob- 
ably leave  no  progeny. 

But  perhaps  the  circumstances  may  change, 
or  the  whole  strain  may  be  dispersed  and  spread 
to  new  localities  with  different  conditions.  Some 
of  the  latter  might  be  found  to  be  favorable  to 
the  robust  gig  as,  or  to  riihrinervis,  which  re- 
quires a  drier  air,  with  rainfall  in  the  spring- 
time and  sunshine  during  the  summer.  It  would 
be  worth  while  to  see  whether  the  climate 
of  California,  where  neither  0.  lamarckiana 
nor  0.  hieMfiis  are  found  wild,  would  not  exactly 


Experimental  Pedigree-Cultures        575 

suit  the  requirements  of  the  new  species  ruhri- 
nervis  and  gigas. 

Note. — Oenotheras  are  native  to  America  and  all 
of  the  species  growing  in  Europe  have  escaped  from 
gardens  directly,  or  may  have  arisen  by  mutation,  or 
by  hybridization  of  introduced  species.  A  fixed 
hybrid  between  0.  cruciata  and  0.  biennis  constituting 
a  species  has  been  in  cultivation  for  many  years. 
The  form  known  as  0.  biennis  in  Europe,  and  used 
by  de  Vries  in  all  of  the  experiments  described  in  these 
lectures,  has  not  yet  been  found  growing  wild  in 
America  and  is  not  identical  with  the  species  bearing 
that  name  among  American  botanists.  Concerning 
this  matter  Professor  de  Vries  writes  under  date  of 
Sept.  12,  1905:  "The  'biennis'  which  I  collected  in 
America  has  proved  to  be  a  motley  collection  of  forms, 
which  at  that  time  I  had  no  means  of  distinguishing. 
No  one  of  them,  so  far  as  they  are  now  growing  in 
my  garden  is  identical  with  our  biennis  of  the  sand 
dunes."  The  same  appears  to  be  the  case  with 
0.  muricata.  Plants  from  the  Northeastern  American 
seaboard,  identifiable  with  the  species  do  not  entirely 
agree  with  those  raised  from  seed  received  from 
Holland. 

0.  Lamarckiana  has  not  been  found  growing  wild 
in  America  in  recent  years  although  the  evidence  at 
hand  seems  to  favor  the  conclusion  that  it  was  seen 
and  collected  in  the  southern  states  in  the  last  century. 
(See  MacDougal,  Vail,  Shull,  and  Small.  Mutants 
and  Hybrids  of  the  Oenotheras.  Publication  24. 
Carnegie  Institution.     Washington,  D.  C,  1905.) 

Editor. 


Lecture  XX 

THE   ORIGIN  OF  WILD  SPECIES  AND  VARIETIES 

New  species  and  varieties  occur  from  time  to 
time  in  the  wild  state.  Setting  aside  all  theo- 
retical conceptions  as  to  the  common  origin  of 
species  at  large,  the  undoubted  fact  remains  that 
new  forms  are  sometimes  met  with.  In  the  case 
of  the  peloric  toad-flax  the  mutations  are  so 
numerous  that  they  seem  to  be  quite  regular. 
The  production  of  new  species  of  evening-prim- 
roses was  observed  on  the  field  and  afterwards 
duplicated  in  the  garden.  There  is  no  reason 
to  think  that  these  cases  are  isolated  instances. 
Quite  on  the  contrary  they  seem  to  be  the  pro- 
totypes of  repeated  occurrences  in  nature. 

If  this  conception  is  granted,  the  question  at 
once  arises,  how  are  we  to  deal  with  analogous 
cases,  when  fortune  offers  them,  and  what  can 
we  expect  to  learn  from  them? 

A  critical  study  of  the  existing  evidence  seems 
to  be  of  great  importance  in  order  to  ascertain 
the  best  way  of  dealing  with  new  facts,  and  of 
estimating  the  value  of  the  factors  concerned. 

576 


Origin  of  Wild  Species  577 

It  is  manifest  that  we  must  be  very  careful  and 
conservative  in  dealing  with  new  facts  that  are 
brought  to  our  attention,  and  every  effort  should 
be  made  to  bring  additional  evidence  to  light. 
Many  vegetable  anomalies  are  so  rare  that 
they  are  met  with  only  by  the  purest 
chance,  and  are  then  believed  to  be  wholly 
new.  When  a  white  variety  of  some  common 
plant  is  met  with  for  the  first  time  we  generally 
assume  that  it  originated  on  that  very  spot 
and  only  a  short  time  previously.  The  discov- 
ery of  a  second  locality  for  the  same  variety  at 
once  raises  the  question  as  to  a  common  origin 
in  the  two  instances.  Could  not  the  plants  of 
the  second  locality  have  arisen  from  seeds 
transported  from  the  first! 

White  varieties  of  many  species  of  blue-bells 
and  gentians  are  found  not  rarely,  white-flower- 
ing plants  of  heather,  both  of  Erica  Tetralix  and 
Calluna  vulgaris  occur  on  European  heaths; 
white  flowers  of  Brunella  vulgaris,  Ononis  re- 
pens,  Thymus  vulgaris  and  others  may  be  seen 
in  many  localities  in  the  habitats  of  the  colored 
species.  Pelories  of  labiates  seem  to  occur 
often  in  Austria,  but  are  rare  in  Holland ;  white 
bilberries  {Vaccinium  Myrtillus)  have  many 
known  localities  throughout  Europe,  and  nearly 
all  the  berry-bearing  species  in  the  large  heath- 
family  are  recorded  as  having  white  varieties. 


578  Mutations 

Are  we  to  assume  a  single  origin  for  all  the 
representatives  of  such  a  variety,  as  we  have 
done  customarily  for  all  the  representatives  of 
a  wild  species  1  Or  can  the  same  mutation  have 
been  repeated  at  different  times  and  in  distant 
localities?  If  a  distinct  mutation  from  a  given 
species  is  once  possible,  why  should  it  not  occur 
twice  or  thrice? 

A  variety  which  seems  to  be  new  to  us  may 
only  appear  so,  because  the  spot  where  it  grows 
had  hitherto  escaped  observation.  Lychnis 
preslii  is  a  smooth  variety  of  Lychnis  diurna 
and  was  observed  for  the  first  time  in  the  year 
1842  by  Sekera.  It  grew  abundantly  in  a  grove 
near  Miinchengratz  in  southern  Hungary.  It 
was  accompanied  by  the  ordinary  hairy  type  of 
the  species.  Since  then  it  has  been  observed  to 
be  quite  constant  in  the  same  locality,  and  some 
specimens  have  been  collected  for  me  there  late- 
ly by  Dr.  Nemec,  of  Prague.  No  other  native 
localities  of  this  variety  have  been  discovered, 
and  there  can  be  no  doubt  that  it  must  have 
arisen  from  the  ordinary  campion  near  the  spot 
where  it  still  grows.  But  this  change  may  have 
taken  place  some  years  before  the  first  discov- 
ery, or  perhaps  one  or  more  centuries  ago. 
This  could  only  be  known  if  it  could  be  proved 
that  the  locality  had  been  satisfactorily  investi- 
gated previously,  and  that  the  variety  had  not 


Origin  of  Wild  Species  579 

been  met  with.  Even  in  this  case  only  some- 
thing would  be  discovered  about  the  time  of  the 
change,  but  nothing  about  its  real  nature. 

So  it  is  in  many  cases.  If  a  variety  is  ob- 
served in  a  number  of  specimens  at  the  time 
of  its  first  discovery,  and  at  a  locality  not 
studied  previously,  it  takes  the  aspect  of  an  old 
form  of  limited  distribution,  and  little  can  be 
learned  as  to  the  circumstances  under  which  it 
arose.  If  on  the  contrary  it  occurs  in  very 
small  numbers  or  perhaps  even  in  a  single  in- 
dividual, and  if  the  spot  where  it  is  found  is 
located  so  that  it  could  hardly  have  escaped  pre- 
vious observation,  then  the  presumption  of  a  re- 
cent origin  seems  justified. 

What  has  to  be  ascertained  on  such  occasions 
to  give  them  scientific  value?  Three  points 
strike  me  as  being  of  the  highest  importance. 
First,  the  constancy  of  the  new  type;  secondly, 
the  occurrence  or  lack  of  intermediates,  and  last, 
but  not  least,  the  direct  observation  of  a  re- 
peated production. 

The  first  two  points  are  easily  ascertained. 
Whether  the  new  type  is  linked  with  its  more 
common  supposed  ancestor  by  intermediate 
steps  is  a  query  which  at  once  strikes  the  bota- 
nist. It  is  usually  recorded  in  such  cases,  and 
we  may  state  at  once  that  the  general  result  is, 
that  such  intermediates  do  not  occur.     This  is 


580  Mutations 

of  the  highest  importance  and  admits  of  only 
two  explanations.  One  is  that  intermediates 
may  be  assumed  to  have  preceded  the  existent 
developed  form,  and  to  have  died  out  after- 
wards. But  why  should  they  have  done  so, 
especially  in  cases  of  recent  changes?  On  the 
other  hand  the  intermediates  may  be  lacking 
because  they  have  never  existed,  the  change 
having  taken  place  by  a  sudden  leap,  such  as  the 
mutations  described  in  our  former  lectures.  It 
is  manifest  that  the  assumption  of  hypothetical 
intermediates  could  only  gain  some  probability 
if  they  had  been  found  in  some  instance.  Since 
they  do  not  occur,  the  hypothesis  seems  wholly 
unsupported. 

The  second  point  is  the  constancy  of  the  new 
type.  Seeds  should  be  saved  and  sown.  If  the 
plant  fertilizes  itself  without  the  aid  of  insects, 
as  do  some  evening-primroses,  the  seed  saved 
from  the  native  locality  may  prove  wholly  pure, 
and  if  it  does  give  rise  to  a  uniform  progeny  the 
constancy  of  the  race  may  be  assumed  to  be 
proved,  provided  that  repeated  trials  do  not 
bring  to  light  any  exceptions.  If  the  offspring 
shows  more  than  one  type,  cross-fertilization  is 
always  to  be  looked  to  as  the  most  probable 
cause,  and  should  be  excluded,  in  order  to  sow 
pure  seeds.  Garden-experiments  of  this  kind, 
and  repeated  trials,  should  always  be  combined 


Origin  of  Wild  Species  581 

with  the  discovery  of  a  presumed  mutation.  In 
many  instances  the  authors  have  realized  the 
importance  of  this  point,  and  new  types  have 
been  found  constant  from  the  very  beginning. 
Many  cases  are  known  which  show  no  rever- 
sions and  even  no  partial  reversions.  This  fact 
throws  a  distinct  light  on  our  first  point,  as  it 
makes  the  hypothesis  of  a  slow  and  gradual  de- 
velopment still  more  improbable. 

My  third  point  is  of  quite  another  nature  and 
has  not  as  yet  been  dealt  with.  But  as  it  ap- 
peals to  me  as  the  very  soul  of  the  problem, 
it  seems  necessary  to  describe  it  in  some  detail. 
It  does  not  refer  to  the  new  type  itself,  nor  to 
any  of  its  morphologic  or  hereditary  attributes, 
but  directly  concerns  the  presumed  ancestors 
themselves. 

The  peloric  toad-flax  in  my  experiment  was 
seen  to  arise  thrice  from  the  same  strain.  Three 
different  individuals  of  my  original  race  showed 
a  tendency  to  produce  peloric  mutations,  and 
they  did  so  in  a  number  of  their  seeds,  exactly 
as  the  mutations  of  the  evening-primroses  were 
repeated  nearly  every  year.  Hence  the  infer- 
ence, that  whenever  we  find  a  novelty  which  is 
really  of  very  recent  date,  the  parent-strain 
which  has  produced  it  might  still  be  in  existence 
on  the  same  spot.  In  the  case  of  shrubs  or 
perennials  the  very  parents  might  yet  be  found. 


582  Mutations 

But  it  seems  probable,  and  is  especially  proved 
in  the  case  of  the  evening-primroses,  that  all 
or  the  majority  of  the  representatives  of  the 
whole  strain  have  the  same  tendency  to  mutate. 
If  this  were  a  general  rule,  it  would  suffice  to 
take  some  pure  seeds  from  specimens  of  the 
presumed  parents  and  to  sow  and  multiply  the 
individuals  to  such  an  extent  that  the  mutation 
might  have  a  chance  to  be  repeated. 

Unfortunately,  this  has  not  as  yet  been  done, 
but  in  my  opinion  it  should  be  the  first  effort  of 
any  one  who  has  the  good  luck  to  discover  a  new 
wild  mutation.  Specimens  of  the  parents 
should  be  transplanted  into  a  garden  and  fertil- 
ized under  isolated  conditions.  Seeds  saved 
from  the  wild  plant  would  have  little  worth,  as 
they  might  have  been  partly  fertilized  by  the 
new  type  itself. 

After  this  somewhat  lengthy  discussion  of  the 
value  of  observations  surrounding  the  discovery 
of  new  wild  mutations,  we  now  come  to  the  de- 
scription of  some  of  the  more  interesting  cases. 
As  a  first  example,  I  will  take  the  globular- 
fruited  shepherd's  purse,  described  by  Solms- 
Laubach  as  Capsella  heegeri.  Professor 
Heeger  discovered  one  plant  with  deviating 
fruits,  in  a  group  of  common  shepherd's  purses 
in  the  market-place  near  Landau  in  Germany, 
in  the  fall  of  1897.     They  were  nearly  spher- 


Origin  of  Wild  Species  58 


Q 


ical,  instead  of  fiat  and  purse-shaped.  Their 
valves  were  thick  and  fleshy,  while  those  of  the 
ordinary  form  are  membranaceous  and  dry. 
The  capsules  hardly  opened  and  therefore  dif- 
fered in  this  point  from  the  shepherd's  purse, 
which  readily  loosens  both  its  valves  as  soon  as 
it  is  ripe. 

Only  one  plant  was  observed ;  whence  it  came 
could  not  be  determined,  nor  whether  it  had 
arisen  from  the  neighboring  stock  of  Capsella 
or  not.  The  discoverer  took  some  seed  to  his 
garden  and  sent  some  to  the  botanical  garden 
at  Strassburg,  of  which  Solms-Laubach  is  the 
director.  The  majority  of  the  seeds  of  course 
were  sowed  naturally  on  the  original  spot.  The 
following  year  some  of  the  seeds  germinated 
and  repeated  the  novelty.  The  leaves,  stems  and 
flowers  were  those  of  the  common  shepherd's 
purse,  but  no  decision  could  be  reached  concern- 
ing the  type  of  this  generation  before  the  first 
flowers  had  faded  and  the  rounded  capsules  had 
developed.  Then  it  was  seen  that  the  heegeri 
came  true  from  seed.  It  did  so  both  in  the 
gardens  and  on  the  market-place,  where  it  was 
observed  to  have  multiplied  and  spread  in  some 
small  measure.  The  same  was  noted  the  fol- 
lowing year,  but  then  the  place  was  covered  with 
gravel  and  all  the  plants  destroyed.  It  is  not 
recorded  to  have  been  seen  wild  since. 


584  Mutations 

Intermediate  forms  have  not  been  met  with. 
Some  slight  reversions  may  occur  in  the  autumn 
on  the  smallest  and  weakest  lateral  branches. 
Such  reversions,  however,  seem  to  be  very  rare, 
as  I  have  tried  in  vain  to  produce  them  on  large 
and  richly  branched  individuals,  by  applying  all 
possible  inducements  in  the  form  of  manure 
and  of  cutting,  to  stimulate  the  production  of 
successive  generations  of  weaker  side  branches. 
This  constancy  was  proved  by  the  experi- 
ments of  Solms-Laubach,  which  I  have  repeated 
in  my  own  garden  during  several  years  with 
seed  received  from  him.  No  atavists  or  deviat- 
ing specimens  have  been  found  among  many 
hundreds  of  flowering  plants. 

It  is  important  to  note  that  within  the  family 
of  the  crucifers  the  form  of  the  capsule  and  the 
attributes  of  the  valves  and  seeds  are  usually 
considered  to  furnish  the  characteristics  of 
genera,  and  this  point  has  been  elucidated  at 
some  length  by  Solms-Laubach.  There  is,  how- 
ever, no  sufficient  reason  to  construe  a  new 
genus  on  the  ground  of  Heeger's  globular- 
fruited  shepherd's  purse;  but  as  a  true  elemen- 
tary species,  and  even  as  a  good  systematic 
species  it  has  proved  itself,  and  as  such  it  is  de- 
scribed by  Solms-Laubach,  who  named  it  in 
honor  of  its  discoverer. 

Exactly    analogous    discoveries    have    been 


Origin  of  Wild  Species  585 

made  from  time  to  time  with  other  plants  by 
different  writers.  Near  Wageningen,  in  Hol- 
land, I  found  Stellaria  Holostea  apetala  in  the 
year  1889,  and  near  Horn  in  Lippe  (Germany) 
Capsella  Biirsa-pastoris  apetala,  both  in  a  very 
few  specimens  on  a  single  spot.  Whether  these 
were  mutations  or  introductions  remains  of 
course  uncertain.  About  the  same  time  I  dis- 
covered near  Hilversum  in  Holland  a  smooth 
variety  of  the  evening  campion,  Lychnis  vesper- 
Una,  forming  a  very  small  group  of  individuals 
in  a  field,  where  the  hairy  type  was  common. 
It  was  sown  in  my  garden  and  proved  pure  and 
constant,  without  intermediates.  As  the  local- 
ity had  been  repeatedly  and  carefully  investi- 
gated by  me,  I  trust  to  be  justified  in  the  asser- 
tion that  I  gathered  the  very  first  individuals  of 
the  variety.  The  stock  soon  was  overgrown  by 
surrounding  shrubs  and  died  out,  and  now  only 
the  cultivated  offspring  are  available,  as  in  the 
case  of  Heeger's  shepherd's  purse. 

A  very  curious  instance  of  spontaneous  muta- 
tions is  afforded  by  a  peculiarity  of  some  even- 
ing-primroses and  their  allies.  This  peculiarity 
is  shown  by  the  petals  remaining  minute  and 
assuming  a  linear  shape.  The  character  is  de- 
veloped as  a  specific  one  in  Oenothera  cruciata. 
This  plant  owes  its  name  to  the  shape  of  the 
petals,  which  form  a  slender  cross  in  the  flower, 


586  Mutations 

instead  of  displaying  a  bright  yellow  cup. 
0,  cruciata  grows  in  the  Adirondack  Mountains, 
in  the  states  of  New  York  and  Vermont,  and 
seems  to  be  abundant  there.  It  has  been  intro- 
duced into  botanical  gardens  and  yielded  a  num- 
ber of  hybrids,  especially  with  0.  biennis  and  0. 
lamarchiana,  and  the  narrow  petals  of  the 
parent-species  may  be  met  with  in  combination 
with  the  stature  and  vegetative  characteristics 
of  these  last  named  species.  0.  cruciata  has  a 
purple  foliage,  while  biennis  and  lamarckiana 
are  green,  and  many  of  the  hybrids  may  in- 
stantly be  recognized  by  their  purple  color. 

The  curious  attribute  of  the  petals  is  not  to  be 
considered  simply  as  a  reduction  in  size.  On 
anatomical  inquiry  it  has  been  found  that  these 
narrow  petals  bear  some  characteristics  which, 
on  the  normal  plants,  are  limited  to  the  calyx. 
Stomata  and  hairs,  and  the  whole  structure  of 
the  surface  and  inner  tissues  on  some  parts  of 
these  petals  are  exactly  similar  to  those  of  the 
calyx,  while  on  others  they  have  retained  the 
characteristics  of  petals.  Sometimes  there 
may  even  be  seen  by  the  naked  eye  green  longi- 
tudinal stripes  of  calyx-like  structure  alter- 
nating with  bright  yellow  petaloid  parts.  For 
these  reasons  the  cruciata  character  may  be  con- 
sidered as  a  case  of  sepalody  of  the  petals,  or  of 
the  petals  being  partly  converted  into  sepals. 


Origin  of  Wild  Species  587 

It  is  worth  while  to  note  that  as  a  monstrosity 
this  occurrence  is  extremely  rare  throughout  the 
whole  vegetable  kingdom,  and  only  very  few 
instances  have  been  recorded. 

Two  cases  of  sudden  mutations  have  come  to 
my  knowledge,  producing  this  same  anomaly  in 
allied  species.  One  has  been  already  alluded  to ; 
it  pertains  to  the  common  evening-primrose  or 
Oenothera  biennis,  and  one  is  a  species  belong- 
ing to  another  genus  of  the  same  family,  the 
great  hairy  willow-herb  or  Epilohium  hirsutum. 
I  propose  to  designate  both  new  forms  by  the 
varietal  name  of  cruciata,  or  cruciatum. 

Oenothera  biennis  cruciata  was  found  in  a 
native  locality  of  the  0.  biennis  itself.  It  con- 
sisted, of  only  one  plant,  showing  in  all  its  flow- 
ers the  cruciata  marks.  In  all  other  respects  it 
resembled  wholly  the  biennis,  especially  in  the 
pure  green  color  of  its  foliage,  which  at  once 
excluded  all  suspicion  of  hybrid  origin  with  the 
purple  0.  cruciata.  Moreover  in  our  country 
this  last  occurs  onlv  in  the  cultivated  state  in 
botanical  gardens. 

Intermediates  were  not  seen,  and  as  the  plant 
bore  some  pods,  it  was  possible  to  test  its  con- 
stancy. I  raised  about  500  plants  from  its  seeds, 
out  of  which  more  than  100  flowered  in  the  first 
year.  The  others  were  partly  kept  through  tho 
winter  and  flowered  next  year.     Seeds  saved  in 


588  Mutations 

both  seasons  were  sown  on  a  large  scale.  Both 
the  first  and  the  succeeding  generations  of 
the  offspring  of  the  original  plant  came  true 
without  any  exception.  Intermediates  are 
often  found  in  hybrid  cultures,  and  in  them  the 
character  is  a  very  variable  one,  but  as  yet  they 
were  not  met  with  in  progeny  of  this  mutant. 
All  these  plants  were  exactly  like  0.  biennis, 
with  the  single  exception  of  their  petals. 

Epilobium  Mrsutum  cruciatum  was  discov- 
ered by  John  Rasor  near  Woolpit,  Bury  St.  Ed- 
munds, in  England.  It  flowered  in  one  spot, 
producing  about  a  dozen  stems,  among  large 
quantities  of  the  parent-species,  which  is  very 
common  there,  as  it  is  elsewhere  in  Europe. 
This  species  is  a  perennial,  multiplying  itself  by 
underground  runners,  and  the  stems  of  the 
new  variety  were  observed  to  stand  so  close  to 
each  other  that  they  might  be  considered  as  the 
shoots  of  one  individual.  In  this  case  this  spec- 
imen might  probably  be  the  original  mutant,  as 
the  variety  had  not  been  seen  on  that  spot  in 
previous  years,  even  as  it  has  not  been  found 
elsewhere  in  the  vicinity. 

Intermediates  were  not  observed,  though  the 
difference  is  a  very  striking  one.  In  the  cru- 
ciate flowers  the  broad  and  bright  purple  petals 
seem  at  first  sight  to  be  wholly  wanting.  They 
are  too  weak  to  expand  and  to  reflex  the  calyx 


Origin  of  Wild  Species  589 

as  in  the  normal  flowers  of  the  species.  The 
sepals  adhere  to  one  another,  and  are  only 
opened  at  their  summit  by  the  protruding  pis- 
tils. Even  the  stamens  hardly  come  to  light. 
At  the  period  of  full  bloom  the  flowers  convey 
only  the  idea  of  closed  buds  crowned  by  the  con- 
spicuous white  cross  of  the  stigma.  Any  inter- 
mediate form  would  have  at  once  betrayed  itself 
by  larger  colored  petals,  coming  out  of  the 
calyx-sheath.  The  cruciate  petals  are  small 
and  linear  and  greenish,  recalling  thereby  the 
color  of  the  sepals. 

Mr.  Rasor  having  sent  me  some  flowers  and 
some  ripe  capsules  of  his  novelty,  I  sowed  the 
latter  in  my  experimental  garden,  where  the 
plant  flowered  in  large  numbers  and  with  many 
thousands  of  flowers  both  in  1902  and  1903. 
All  of  these  plants  and  all  of  these  flowers  re- 
peated the  cruciate  type  exactly,  and  not  the 
slighest  impurity  or  tendency  to  partial  rever- 
sion has  been  observed. 

Thus  true  and  constant  cruciate  varieties 
have  been  produced  from  accidentally  observed 
initial  plants,  and  because  of  their  very  curious 
characters  they  will  no  doubt  be  kept  in 
botanical  gardens,  even  if  they  should  event- 
ually become  lost  in  their  native  localities. 

At  this  point  I  might  note  another  observation 
made  on  the  wild  species  of  Oenothera  cruciata 


590  Mutations 

from  the  Adirondacks.  Through  the  kindness 
of  Dr.  MacDougal,  of  the  New  York  Botanical 
Garden,  I  received  seeds  from  Sandy  Hill  near 
Lake  George.  When  the  plants,  grown  from 
these  seeds,  flowered,  they  were  not  a  uniform 
lot,  but  exhibited  two  distinct  types.  Some  had 
linear  petals  and  thin  flower-buds,  and  in 
others  the  petals  were  a  little  broader  and  the 
buds  more  swollen.  The  difference  was  small, 
but  constant  on  all  the  flowers,  each  single  plant 
clearly  belonging  to  one  or  the  other  of  the  two 
types.  Probably  two  elementary  species  were 
intermixed  here,  but  whether  one  is  the  sys- 
tematic type  and  the  other  a  mutation,  remains 
to  be  seen. 

Nor  seem  these  two  types  to  exhaust  the  range 
of  variability  of  Oenothera  cruciata.  Dr.  B.  L. 
Eobinson  of  Cambridge,  Mass.,  had  the  kind- 
ness to  send  me  seeds  from  another  locality  in 
the  same  region.  The  seeds  were  collected  in 
New  Hampshire  and  in  my  garden  produced  a 
true  and  constant  cruciata,  but  with  quite  differ- 
ent secondarv  characters  from  both  the  afore- 
said  varieties.  The  stems  and  flower-spikes  and 
even  the  whole  foliage  were  much  more  slender, 
and  the  calyx-tubes  of  the  flowers  were  notice- 
ably more  elongated.  It  seems  not  improbable 
that  Oenothera  cruciata  includes  a  group  of 
lesser  unities,  and  may  prove  to  comprise  a 


Origin  of  Wild  Species  591 

swarm  of  elementary  species,  while  the  original 
strain  might  even  now  be  still  in  a  condition  of 
mutability.  A  close  scrutiny  in  the  native  re- 
gion is  likely  to  reveal  many  unexpected 
features. 

A  very  interesting  novelty  has  already  been 
described  in  a  former  lecture.  It  is  the  Xan- 
thium  wootoni,  discovered  in  the  region  about 
Las  Vegas,  New  Mexico,  by  T.  D.  A.  Cockerell. 
It  is  similar  in  all  respects  to  X.  commune^  but 
the  burrs  are  more  slender  and  the  prickles 
much  less  numerous,  and  mostlv  stouter  at  their 
base.  It  grows  in  the  same  localities  as  the 
X.  commune,  and  is  not  recorded  to  occur  else- 
where. Whether  it  is  an  old  variety  or  a  recent 
mutation  it  is  of  course  impossible  to  decide. 
In  a  culture  made  in  my  garden  from  the  seed 
sent  me  by  Mr.  Cockerell,  I  observed  (1903)  that 
both  forms  had  a  subvariety  with  brownish 
foliage,  and,  besides  this,  one  of  a  pure  green. 
Possibly  this  species,  too,  is  still  in  a  mutable 
condition. 

Perhaps  the  same  may  be  asserted  concerning 
the  beautiful  shrub.  Hibiscus  Moscheutos,  ob- 
served in  quite  a  number  of  divergent  types  by 
John  W.  Harshberger.  They  grew  in  a  small 
meadow  at  Seaside  Park,  New  Jersey,  in  a 
locality  which  had  been  undisturbed  for  years. 
They  differed  from  each  other  in  nearlv  all  the 


592  Mutations 

organs,  in  size,  in  the  diameter  of  the  stems, 
which  were  woody  in  some  and  more  fleshy  in 
others,  in  the  shape  of  the  foliage  and  in  the 
flowers.  More  than  twenty  types  could  be  dis- 
tinguished and  seeds  were  saved  from  a  num- 
ber of  them,  in  order  to  ascertain  whether  they 
are  constant,  or  whether  perhaps  a  main  stem  in 
a  mutating  condition  might  be  found  among 
them.  If  this  should  prove  to  be  the  case,  the 
relations  between  the  observed  forms  would 
probably  be  analogous  to  those  between  the  0. 
lamarcMana  and  its  derivatives. 

Many  other  varieties  have  sprung  from  the 
type-species  under  similar  conditions  from  time 
to  time.  A  fern-leaved  mercury,  Mercurialis 
annua  laciniata,  was  discovered  in  the  year  1719 
by  Merchant  The  type  was  quite  new  at  the 
time  and  mamtained  itself  during  a  series  of 
years.  The  yellow^  deadly  nightshade  or  Atropa 
Belladonna  lutea  wa^s  found  about  1850  in  the 
Black  Forest  in  Germciny  in  a  single  spot,  and 
has  since  been  multiplied  by  seeds.  It  is  now 
dispersed  in  botanical  gardens,  and  seems  to  be 
quite  constant.  A  dwarf  variety  of  a  bean, 
Phaseolus  lunatus,  was  obsei-ved  to  spring  from 
the  ordinary  type  by  a  sudden  leap  about  1895 
by  W.  W.  Tracy,  and  many  similar  cases  could 
be  given. 

The  annual  habit  is  not  very  favorable  for 


Origin  of  Wild  Species  593 

the  discovery  of  new  forms  in  the  wild  state. 
New  varieties  may  appear,  but  may  be  crowded 
out  the  first  year.  The  chances  are  much 
greater  with  perennials,  and  still  greater  with 
shrubs  or  trees.  A  single  aberrant  specimen 
may  live  for  years  and  even  for  centuries,  and 
under  such  conditions  is  pretty  sure  to  be  dis- 
covered sooner  or  later.  Hence  it  is  no  won- 
der that  many  such  cases  are  on  record.  They 
have  this  in  common  that  the  original  plant 
of  the  variety  has  been  found  among  a  vast 
majority  of  representatives  of  the  correspond- 
ing species.  Nothing  of  course  is  directly 
known  about  its  origin.  Intermediate  links 
have  as  a  rule  been  wanting,  and  the  seeds, 
which  have  often  been  sown,  have  not  yielded 
reliable  results,  as  no  care  was  taken  to  pre- 
serve the  blossoms  from  intercrossing  with  their 
parent-forms. 

Stress  should  be  laid  upon  one  feature  of 
these  curious  occurrences.  Eelatively  often 
the  same  novelty  has  been  found  twice  or  thrice, 
or  even  more  frequently,  and  under  conditions 
which  make  it  very  improbable  that  any  relation 
between  such  occurrences  might  exist.  The 
same  mutation  must  have  taken  place  more  than 
once  from  the  same  main  stem. 

The  most  interesting  of  these  facts  are  con- 
nected with  the  origin  of  the  purple  beech,  which 


594  Mutations 

is  now  so  universally  cultivated.  I  take  the  fol- 
lowing statements  from  an  interesting  historical 
essay  of  Prof.  Jaggi.  He  describes  three  orig- 
inal localities.  One  is  near  the  Swiss  village, 
Buch  am  Irchel,  and  is  located  on  the  Stamm- 
berg.  During  the  17th  century  five  purple 
beeches  are  recorded  to  have  grown  on  this  spot. 
Four  of  them  have  died,  but  one  is  still  alive. 
Seedlings  have  germinated  around  this  little 
group,  and  have  been  mostly  dug  up  and  trans- 
planted into  neighboring  gardens.  Nothing  is 
known  about  the  real  origin  of  these  plants,  but 
according  to  an  old  document,  it  seems  that 
about  the  year  1190  the  purple  beeches  of  Buch 
were  already  enjoying  some  renown,  and  at- 
tracting large  numbers  of  pilgrims,  owing  to 
some  old  legend.  The  church  of  Embrach  is  said 
to  have  been  built  in  connection  with  this  legend, 
and  was  a  goal  for  pilgrimages  during  many 
centuries. 

A  second  native  locality  of  the  purple  beech 
is  found  in  a  forest  near  Sondershausen  in 
Thiiringen,  Germany,  where  a  fine  group  of 
these  trees  is  to  be  seen.  They  were  mentioned 
for  the  first  time  in  the  latter  half  of  the 
eighteenth  century,  but  must  have  been  old  spec- 
imens long  before  that  time.  The  third  locality 
seems  to  be  of  much  later  origin.  It  is  a  forest 
near  Roveredo  in  South  Tyrol,  where  a  new 


Origin  of  Wild  Species  595 

university  is  being  erected.  It  is  only  a  century 
ago  that  the  first  specimens  of  the  purple  beech 
were  discovered  there. 

As  it  is  very  improbable  that  the  two  last 
named  localities  should  have  received  their  pur- 
ple beeches  from  the  first  named  forest,  it  seems 
reasonable  to  assume  that  the  variety  must  have 
been  produced  at  least  thrice. 

The  purple  beech  is  now  exceedingly  common 
in  cultivation.  But  Jaggi  succeeded  in  showing 
that  all  the  plants  owe  their  origin  to  the  orig- 
inal trees  mentioned  above,  and  are,  including 
nearly  all  cultivated  specimens  with  the  sole  ex- 
ception of  the  vicinity  of  Buch, probably  derived 
from  the  trees  in  Thiiringen.  They  are  easily 
multiplied  by  grafting,  and  come  true  from 
seed,  at  least  often,  and  in  a  high  proportion. 
Wiether  the  original  trees  would  yield  a 
pure  progeny  if  fertilized  hj  their  own  pol- 
len has.  as  yet  not  been  tested.  The  young  seed- 
lings have  purple  seed-leaves,  and  may  easily  be 
selected  by  this  character,  but  they  seem  to 
be  always  subjected  in  a  large  measure  to 
vicinism. 

Many  other  instances  of  trees  and  shrubs, 
found  in  accidental  specimens  constituting  a 
new  variety  in  the  wild  state,  might  be  given. 
The  oak-leaved  beech  has  been  found  in  a  forest 
of  Lippe-Detmold  in  Germany  and  near  Ver- 


596  Mutations 

sailles,  whence  it  was  introduced  into  horticul- 
ture by  Carriere.  Similarly  divided  and  cleft 
leaves  seem  to  have  occurred  more  often  in  the 
wild  state,  and  cut-leaved  hazels  are  recorded 
from  Kouen  in  France,  birches  and  alders  from 
Sweden  and  Lapland,  where  both  are  said  to 
have  been  met  with  in  several  forests.  The 
purple  barberry  was  found  about  1830  by  Ber- 
tin,  near  Versailles.  Weeping  varieties  of 
ashes  were  found  wild  in  England  and  in  Ger- 
many, and  broom-like  oaks,  Qiiercus  pedun- 
culata  fastigiata,  are  recorded  from  Hessen- 
Darmstadt,  Calabria,  the  Pyrenees  and  other 
localities.  About  the  real  origin  of  all  these 
varieties  nothing  is  definitely  known. 

The  '^  single-leaved  "  strawberry  is  a  variety 
often  seen  in  botanical  gardens,  as  it  is  easily 
propagated  by  its  runners.  It  was  discovered 
wild  in  Lapland  at  the  time  of  Linnaeus,  and 
appeared  afterwards  unexpectedly  in  a  nursery 
near  Versailles.  This  happened  about  the  year 
1760  and  Duchesne  tested  it  from  seeds  and 
found  it  constant.  This  strain,  however,  seems 
to  have  died  out  before  the  end  of  the  18th  cen- 
tury. In  a  picture  painted  by  Holbein  (1495- 
1543),  strawberry  leaves  can  be  seen  agreeing 
exactly  with  the  monophyllous  type.  The  va- 
riety may  thus  be  assumed  to  have  arisen  inde- 


Origin  of  Wild  Species  597 

pendently  at  least  thrice,  at  dilt'erent  periods 
and  in  distant  localities. 

From  all  these  statements  and  a  good  many 
others  which  can  be  found  in  horticultural  and 
botanical  literature,  it  may  be  inferred  that 
mutations  are  not  so  very  rare  in  nature  as  is 
often  supposed.  Moreover  we  may  conclude 
that  it  is  a  general  rule  that  they  are  neither 
preceded  nor  accompanied  by  intermediate 
steps,  and  that  they  are  ordinarily  constant 
from  seed  from  the  first. 

Why  then  are  they  not  met  with  more  often? 
In  my  opinion  it  is  the  struggle  for  life  which  is 
the  cause  of  this  apparent  rarity ;  which  is  noth- 
ing else  than  the  premature  death  of  all  the  in- 
dividuals that  so  vary  from  the  common  type  of 
their  species  as  to  be  incapable  of  development 
under  prevailing  circumstances.  It  is  obvious- 
ly without  consequence  whether  these  deviations 
are  of  a  fluctuating  or  of  a  mutating  nature. 
Hence  we  may  conclude  that  useless  mutations 
will  soon  die  out  and  will  disappear  without 
leaving  any  progeny.  Even  if  they  are  pro- 
duced again  and  again  by  the  same  strain,  but 
under  the  same  unfavorable  conditions,  there 
will  be  no  appreciable  result. 

Thousands  of  mutations  may  perhaps  take 
place  yearly  among  the  plants  of  our  immediate 
vicinity  without  any  chance  of  being  discovered. 


598  Mutations 

We  are  trained  to  the  appreciation  of  the  dif- 
ferentiating marks  of  systematic  species.  When 
we  have  succeeded  in  discerning  these  as  given 
by  our  local  flora  lists,  we  rest  content.  Meet- 
ing them  again  we  are  in  the  habit  of  greeting 
them  with  their  proper  names.  Such  is  the 
satisfaction  ensuing  from  this  knowledge  that 
we  do  not  feel  any  inclination  for  further  in- 
quiry. Striking  deviations,  such  as  many 
varietal  characters,  may  be  remarked,  but  then 
they  are  considered  as  being  of  only  secondary 
interest.  Our  minds  are  turned  from  the  deli- 
cately shaded  features  which  differentiate  ele- 
mentary species. 

Even  in  the  native  field  of  the  evening-prim- 
roses, no  botanist  would  have  discovered  the 
rosettes  with  smaller  or  paler  leaves,  constitut- 
ing the  first  signs  of  the  new  species.  Only  by 
the  guidance  of  a  distinct  theoretical  idea  were 
they  discovered,  and  having  once  been  pointed 
out  a  closer  inspection  soon  disclosed  their 
number. 

Variability  seems  to  us  to  be  very  general,  but 
very  limited.  The  limits  however,  are  distinct- 
ly drawn  by  the  struggle  for  existence.  Of 
course  the  chance  for  useful  mutations  is  a  very 
small  one.  We  have  seen  that  the  same  muta- 
tions are  as  a  rule  repeated  from  time  to  time 
by  the  same  species.     Now,  if  a  useful  mutation, 


Origin  of  Wild  Species  599 

or  even  a  wholly  indifferent  one,  might  easily  be 
produced,  it  would  have  been  so,  long  ago,  and 
would  at  the  present  time  simply  exist  as  a  sys- 
tematic variety.  If  produced  anew  somewhere 
the  botanist  would  take  it  for  the  old  variety 
and  would  omit  to  make  any  inquiry  as  to  its 
local  origin. 

Thousands  of  seeds  with  perhaps  wide  circles 
of  variability  are  ripened  each  year,  but  only 
those  that  belong  to  the  existing  old  narrow 
circles  survive.  How  different  would  Nature 
appear  to  us  if  she  were  free  to  evolve  all  her 
potentialities ! 

Darwin  himself  was  struck  with  this  lack  of 
harmony  between  common  observations  and  the 
probable  real  state  of  things.  He  discussed 
it  in  connection  with  the  cranesbill  of  the 
Pyrenees  {Geranium  pyrenaicum).  He  de- 
scribed how  this  fine  little  plant, which  has  never 
been  extensively  cultivated,  had  escaped  from  a 
garden  in  Staffordshire  and  had  succeeded  in 
multiplying  itself  so  as  to  occupy  a  large  area. 
In  doing  so  it  had  evidently  found  place  for  an 
uncommonly  large  number  of  plantlets  from  its 
seeds  and  correspondingly  it  had  commenced  to 
vary  in  almost  all  organs  and  qualities  and 
nearly  in  all  imaginable  directions.  It  dis- 
played under  these  exceptional  circumstances  a 
capacity  which  never  had  been  exceeded  and 


600  Mutations 

which  of  course  would  have  remained  concealed 
if  its  multiplication  had  been  checked  in  the  or- 
dinary way. 

Many  species  have  had  occasion  to  invade  new 
regions  and  cover  them  with  hundreds  of  thou- 
sands of  individuals.  First  are  to  be  cited 
those  species  which  have  been  introduced  from 
America  into  Europe  since  the  time  of  Colum- 
bus, or  from  Europe  into  this  country.  Some  of 
them  have  become  very  common.  In  my  own 
country  the  evening-primroses  and  Canada  flea- 
bane  or  Erigeron  canadensis  are  examples,  and 
many  others  could  be  given.  They  should  be 
expected  to  vary  under  these  circumstances  in 
a  larger  degree.  Have  they  done  so?  Mani- 
festly they  have  not  struck  out  useful  new  char- 
acters that  would  enable  their  bearers  to  found 
new  elementary  species.  At  least  none  have 
been  observed.  But  poor  types  might  have 
been  produced,  and  periods  of  mutability  might 
have  been  gone  through  similar  to  that  which  is 
now  under  observation  for  Lamarck's  evening- 
primrose  in  Holland. 

From  this  discussion  we  may  infer  that  the 
chances  of  discovering  new  mutating  species  are 
great  enough  to  justify  the  utmost  efforts  to 
secure  them.  It  is  only  necessary  to  observe 
large  numbers  of  plants,  grown  under  circum- 
stances which  allow  the  best  opportunities  for 


Origin  of  Wild  Species  601 

all  the  seeds.  And  as  nature  affords  such  op- 
portunities only  at  rare  intervals,  we  should 
make  use  of  artificial  methods.  Large  quan- 
tities of  seed  should  be  gathered  from  wild 
plants  and  sowed  under  very  favorable  condi- 
tions, giving  all  the  nourishment  and  space  re- 
quired to  the  young  seedlings.  It  is  recom- 
mended that  they  be  sown  under  glass,  either  in 
a  glass-house  or  protected  against  cold  and  rain 
by  glass-frames.  The  same  lot  of  seed  will  be 
seen  to  yield  twice  or  thrice  as  many  seedlings 
if  thus  protected,  compared  with  what  it  would 
have  produced  when  sown  in  the  field  or  in  the 
garden.  I  have  nearly  wholly  given  up  sowing 
seeds  in  my  garden,  as  circumstances  can  be 
controlled  and  determined  with  greater  ex- 
actitude when  the  sowing  is  done  in  a  glass- 
house. 

The  best  proof  perhaps,  of  the  unfavorable 
influence  of  external  conditions  for  slightly  de- 
teriorated deviations  is  afforded  by  variegated 
leaves.  Many  beautiful  varieties  are  seen  in 
our  gardens  and  parks,  and  even  corn  has  a 
variety  with  striped  leaves.  They  are  easily  re- 
produced, both  by  buds  and  by  seeds,  and  they 
are  the  most  ordinarv  of  all  varietal  deviations. 
They  may  be  expected  to  occur  wild  also.  But 
no  real  variegated  species,  nor  even  good 
varieties  with  this  attribute  occurs  in  nature. 


602  Mutations 

On  the  other  hand  occasional  specimens  with  a 
single  variegated  leaf,  or  with  some  few  of  them, 
are  actually  met  with,  and  if  attention  is  once 
drawn  to  this  question,  perhaps  a  dozen  or  so 
instances  might  be  brought  together  in  a  sum- 
mer. But  they  never  seem  to  be  capable  of 
further  evolution,  or  of  reproducing  themselves 
sufficiently  and  of  repeating  their  peculiarity  in 
their  progeny.  They  make  their  appearance, 
are  seen  during  a  season,  and  then  disappear. 
Even  this  slight  incompleteness  of  some  spots 
on  one  or  two  leaves  may  be  enough  to  be  their 
doom. 

It  is  a  common  belief  that  new  varieties  owe 
their  origin  to  the  direct  action  of  external 
conditions  and  moreover  it  is  often  assumed  that 
similar  deviations  must  have  similar  causes,  and 
that  these  causes  may  act  repeatedly  in  the  same 
species,  or  in  allied,  or  even  systematically  dis- 
tant genera.  No  doubt  in  the  end  all  things 
must  have  their  causes,  and  the  same  causes 
will  lead  under  the  same  circumstances  to  the 
same  results.  But  we  are  not  justified  in  deduc- 
ing a  direct  relation  between  the  external  con- 
ditions and  the  internal  changes  of  plants. 
These  relations  may  be  of  so  remote  a  nature 
that  they  cannot  as  yet  be  guessed  at.  There- 
fore only  direct  experience  may  be  our  guide. 

Summing  up  the  result  of  our  facts  and  dis- 


Origin  of  Wild  Species  603 

cussions  we  may  state  that  wild  new  elementary 
species  and  varieties  are  recorded  to  have 
appeared  from  time  to  time.  Invariably  this 
happened  by  sudden  leaps  and  without  interme- 
diates. The  mutants  are  constant  when  prop- 
agated by  seed,  and  at  once  constitute  a  new 
race.  In  rare  instances  this  may  be  of  sufficient 
superiority  to  win  a  place  for  itself  in  nature, 
but  more  often  it  has  qualities  which  have  led  to 
its  introduction  into  gardens  as  an  ornamental 
plant  or  into  botanical  gardens  by  reason  of  the 
interest  afforded  by  their  novelty,  or  by  their 
anomaly. 

Many  more  mutations  may  be  supposed  to  be 
taking  place  all  around  us,  but  artificial  sowings 
on  a  large  scale,  combined  with  a  close  exam- 
ination of  the  seedlings  and  a  keen  appreciation 
of  the  slightest  indications  of  deviation  seem 
required  to  bring  them  to  light. 


Lecture  XXI 

MUTATIONS  IN  HORTICULTURE 

It  is  well  known  that  Darwin  based  his  theory 
of  natural  selection  to  a  large  extent  upon  the 
experience  of  breeders.  Natural  and  artificial 
selection  exhibit  the  same  general  features,  yet 
it  was  impossible  in  Darwin's  time  to  make  a 
critical  and  comparative  analysis  of  the  two 
processes. 

In  accordance  with  our  present  conception 
there  is  selection  of  species  and  selection  within 
the  species.  The  struggle  for  life  determines 
which  of  a  group  of  elementary  species  shall  sur- 
vive and  which  shall  disappear.  In  agricultural 
practice  the  corresponding  process  is  usually 
designated  by  the  name  of  variety-testing. 
Within  the  species,  or  within  the  variety,  the 
sieve  of  natural  selection  is  constantly  eliminat- 
ing poor  specimens  and  preserving  those  that 
are  best  adapted  to  live  under  the  given  condi- 
tions. Some  amelioration  and  some  local  races 
are  the  result,  but  this  does  not  appear  to  be  of 
much  importance.     On  the  contrary,  the  selec- 

604 


Mutations  in  Horticulture  605 

tion  within  the  race  holds  a  prominent  place  in 
agriculture,  where  it  is  known  by  the  imposing 
term,  race-breeding. 

Experience  and  methods  in  horticulture  differ 
from  those  in  agriculture  in  many  points. 
Garden-varieties  have  been  tested  and  separated 
for  a  long  time,  but  neither  vegetables  nor 
flowers  are  known  to  exhibit  such  motley  groups 
of  types  as  may  be  seen  in  large  forage  crops. 

New  varieties  which  appear  from  time  to  time 
may  be  ornamental  or  otherwise  in  flowers,  and 
more  or  less  profitable  than  their  parents  in 
vegetables  and  fruits.  In  either  case  the  dif- 
ference is  usually  striking,  or  if  not,  its  culture 
would  be  unprofitable. 

The  recognition  of  useful  new  varieties  being 
thus  made  easy,  the  whole  attention  of  the 
breeder  is  reduced  to  isolating  the  seeds  of  the 
mutants  that  are  to  be  saved  and  sown  separate- 
ly, and  this  process  must  be  repeated  during 
a  few  years,  in  order  to  produce  the  quantity  of 
seed  that  is  needed  for  a  profitable  introduction 
of  the  variety  into  commerce.  In  proportion  to 
the  abundance  of  the  harvest  of  each  year  this 
period  is  shorter  for  some  and  longer  for  other 
species. 

Isolation  in  practice  is  not  so  simple  nor  so 
easy  an  affair  as  it  is  in  the  experimental  gar- 
den.    Hence  we  have  constant  and  nearly  un- 


606  Mutations 

avoidable  cross-fertilizations  with  the  parent- 
form,  or  with  neighboring  varieties,  and  conse- 
quent impurity  of  the  new  strain.  This  impurity 
we  have  called  vicinism,  and  in  a  previous  lec- 
ture have  shown  its  effects  upon  the  horticul- 
tural races  on  one  hand,  and  on  the  other,  on  the 
scientific  value  that  can  be  ascribed  to  the  ex- 
perience of  the  breeder.  We  have  established 
the  general  rule  that  stability  is  seldom  met 
with,  but  that  the  observed  instability  is  always 
open  to  the  objection  of  being  the  result  of  vicin- 
ism. Often  this  last  agency  is  its  sole  cause; 
or  it  may  be  complicated  with  other  factors 
>\^ithout  our  being  able  to  discern  them. 

Though  our  assertion  that  the  practice  of  the 
horticulturist  in  producing  new  varieties  is  lim- 
ited to  isolation,  whenever  chance  affords  them, 
is  theoretically  valid,  it  is  not  always  so.  We 
may  discern  between  the  two  chief  groups  of 
varieties.  The  retrograde  varieties  are  con- 
stant, the  indi\dduals  not  differing  more  from 
one  another  than  those  of  any  ordinary  species. 
The  highly  variable  varieties  play  an  important 
part  in  horticulture.  Double  flowers,  striped 
flowers,  variegated  leaves  and  some  others  yield 
the  most  striking  instances.  Such  forms  have 
been  included  in  previous  lectures  among  the 
ever-sporting  varieties,  because  their  peculiar 
characters  oscillate  between  two  extremes,  viz.: 


Mutations  in  Horticulture  GOT 

the  new  one  of  the  variety  and  the  correspond- 
ing character  of  the  original  species. 

In  such  cases  isolation  is  usuall}^  accompanied 
by  selection:  rarely  has  the  first  of  a  double, 
striped  or  variegated  race  well  filled  or  richly 
striped  flowers  or  highly  spotted  leaves. 
Usually  minor  degrees  of  the  anomaly  are  seen 
first,  and  the  breeder  expects  the  novelty  to  de- 
velop its  features  more  completely  and  more 
beautifully  in  subsequent  generations.  Some 
varieties  need  selection  only  in  the  beginning, 
in  others  the  most  perfect  specimens  must 
be  chosen  every  year  as  seed-bearers.  For 
striped  flowers,  it  has  been  prescribed  by  Vil- 
morin,  that  seeds  should  be  taken  only  from 
those  with  the  smallest  stripes,  because  there  is 
always  reversion.  Mixed  seed  or  seed  from 
medium  types  would  soon  yield  plants  with  too 
broad  stripes,  and  therefore  less  diversified 
flowers. 

In  horticulture,  new  varieties, both  retrograde 
and  ever-sporting,  are  known  to  occur  almost 
yearly.  Nevertheless,  not  every  novelty  of  the 
gardener  is  to  be  considered  as  a  mutation  in 
the  scientific  sense  of  the  word.  First  of  all, 
the  novelties  of  perennial  and  woody  species  are 
to  be  excluded.  Any  extreme  case  of  fluctuat- 
ing variability  may  be  preserved  and  multiplied 
in  the  vegetative  way.     Such  types  are  desig- 


608  Mutations 

nated  in  horticulture  as  varieties,  though  ob- 
viously they  are  of  quite  another  nature  than 
the  varieties  reproduced  by  seed.  Secondly,  a 
large  number,  no  doubt  the  greater  number 
of  novelties,  are  of  hybrid  origin.  Here  we 
may  discern  two  cases.  Hybrids  may  be 
produced  by  the  crossing  of  old  types,  either 
of  two  old  cultivated  forms  or  newlv  intro- 
duced  species,  or  ordinarily  between  an  old 
and  an  introduced  variety.  Such  novelties  are 
excluded  from  our  present  discussion.  Sec- 
ondly, hybrids  may  be  produced  between  a  true, 
new  mutation  and  some  of  the  already  existing 
varieties  of  the  same  species.  Examples  of  this 
obvious  and  usual  practice  will  be  given  further 
on,  but  it  must  be  pointed  out  now  that  by  such 
crosses  a  single  mutation  may  produce  as  many 
novelties  as  there  are  available  varieties  of  the 
same  species. 

Summarizing  these  introductory  remarks  we 
must  lay  stress  on  the  fact  that  only  a  small  part 
of  the  horticultural  novelties  are  real  mutations, 
although  they  do  occur  from  time  to  time.  If 
useful,  they  are  as  a  rule  isolated  and  multiplied, 
and  if  necessary,  improved  by  selection.  They 
are  in  many  instances,  as  constant  from  seed  as 
the  unavoidable  influence  of  vicinism  allows 
them  to  be.  Exact  observations  on  the  origin, 
or  on  the  degree  of  constancy,  are  usually  lack- 


Mutations  in  Horticulture  609 

ing,  the  notes  being  ordinarily  made  for  com- 
mercial purposes,  and  often  only  at  the  date  of 
introduction  into  trade,  when  the  preceding 
stages  of  the  novelty  may  have  been  partly  for- 
gotten. 

With  this  necessary  prelude  I  will  now  give  a 
condensed  survey  of  the  historical  facts  relat- 
ing to  the  origin  of  new  horticultural  varieties. 
An  ample  description  has  been  given  recently 
by  Korshinsky,  a  Russian  writer,  who  has 
brought  together  considerable  historical  mate- 
rial as  evidence  of  the  sudden  appearance  of 
novelties  throughout  the  whole  realm  of  garden- 
plants. 

The  oldest  known,  and  at  the  same  time  one 
of  the  most  accurately  described  mutations  is 
the  origin  of  the  cut-leaved  variety  of  the 
greater  celandine  or  Chelidonium  majus.  This 
variety  has  been  described  either  as  such,  or  as 
a  distinct  species,  called  Chelidonium  laciniatum 
Miller. 

It  is  distinguished  from  the  ordinary  species, 
by  the  leaves  being  cut  into  narrow  lobes,  with 
almost  linear  tips,  a  character  which  is,  as  we 
have  seen  on  a  previous  occasion,  repeated  in 
the  petals.  It  is  at  present  nearly  as  commonly 
cultivated  in  botanical  gardens  as  the  C.  majus, 
and  has  escaped  in  many  localities  and  is  ob- 
served to  thrive  as  readily  as  the  native  wild 


610  Mutations 

plants.  It  was  not  known  until  a  few  years  be- 
fore the  close  of  the  16th  century.  Its  history 
has  been  described  by  the  French  botanist,  Rose. 

It  was  seen  for  the  first  time  in  the  garden  of 
Sprenger,  an  apothecary  of  Heidelberg,  where 
the  C.  majus  had  been  cultivated  for  many 
years.  Sprenger  discovered  it  in  the  year  1590, 
and  was  struck  by  its  peculiar  and  sharply  de- 
viating characters.  He  was  anxious  to  know 
whether  it  was  a  new  plant  and  sent  specimens 
to  Clusius  and  to  Plater,  the  last  of  whom 
transmitted  them  to  Caspar  Bauhin.  These 
botanists  recognized  the  type  as  quite  new  and 
Bauhin  described  it  some  years  afterwards  in 
his  Phytopinax  under  the  name  of  Chelidonium 
ma  jus  foliis  qtiernis,  or  oak-leaved  celandine. 
The  new  variety  soon  provoked  general  interest 
and  was  introduced  into  most  of  the  botanical 
gardens  of  Europe.  It  was  recognized  as  quite 
new,  and  repeated  search  has  been  made  for  it 
in  a  wild  state,  but  in  vain.  No  other  origin 
has  been  discovered  than  that  of  Sprenger 's 
garden.  Afterwards  it  became  naturalized  in 
England  and  elsewhere,  but  there  is  not  the 
least  doubt  as  to  its  derivation  in  all  the  ob- 
served cases. 

Hence  its  origin  at  Heidelberg  is  to  be  con- 
sidered as  historically  proven,  and  it  is  of  course 
only  legitimate  to  assume  that  it  originated  in 


Mutations  in  Horticulture  611 

the  year  1590  from  the  seeds  of  the  C.  majus. 
Nevertheless,  this  was  not  ascertained  by 
Sprenger,  and  some  doubt  as  to  a  possible  intro- 
duction from  elsewhere  might  arise.  If  not, 
then  the  mutation  must  have  been  sudden,  oc- 
curring without  visible  preparation  and  without 
the  appearance  of  intermediates. 

From  the  very  first,  the  cut-leaved  celandine 
has  been  constant  from  seed.  Or  at  least  it  has 
been  propagated  by  seed  largely  and  without 
difficulty.  Nothing,  however,  is  known  about  it 
in  the  first  few  years  of  its  existence.  Later 
careful  tests  were  made  by  Miller,  Rose  and 
others  and  later  by  myself,  which  have  shown 
its  stability  to  be  absolute  and  without  rever- 
sion, and  it  has  probably  been  so  from  the  begin- 
ning. The  fact  of  its  constancy  has  led  to  its 
specific  distinction  by  Miller,  as  varieties 
were  in  his  time  universally,  and  up  to  the  pres- 
ent time  not  rarely,  though  erroneously,  be- 
lieved to  be  less  stable  than  true  species. 

Before  leaving  the  laciniate  celandine  it  is  to 
be  noted  that  in  crosses  with  C.  majus  it  follows 
the  law  of  Mendel,  and  for  this  reason  should 
be  considered  as  a  retrograde  variety,  the  more 
so,  as  it  is  also  treated  as  such  from  a  mor- 
phological point  of  view  by  Stahl  and  others. 

We  now  come  to  an  enumeration  of  those 
cases  in  which  the  date  of  the  first  appearance 


612  Mutations 

of  a  new  horticultural  variety  has  been  record- 
ed, and  I  must  apologize  for  the  necessity  of 
again  quoting  many  variations,  which  have  pre- 
viously been  dealt  with  from  another  point  of 
view.  In  such  cases  I  shall  limit  myself  as 
closely  as  possible  to  historical  facts.  They  have 
been  recorded  chiefly  by  Verlot  and  Carriere, 
who  wrote  in  Paris  shortly  after  the  middle  of 
the  past  century,  and  afterwards  by  Darwin, 
Korshinsky,  and  others.  It  is  from  their  writ- 
ings and  from  horticultural  literature  at  large 
that  the  following  evidence  is  brought  together. 
A  very  well-known  instance  is  that  of  the 
dwarf  variety  of  Tagetes  signat a, which  arose  in 
the  nursery  of  Vilmorin  in  the  year  1860.  It 
was  observed  for  the  first  time  in  a  single  indi- 
vidual among  a  lot  of  the  ordinary  Tagetes  sig- 
nata.  It  was  found  impossible  to  isolate  it,  but 
the  seeds  were  saved  separately.  The  majority 
of  the  offspring  returned  to  the  parental  type, 
but  two  plants  were  true  dwarfs.  From  these 
the  requisite  degree  of  purity  for  commercial 
purposes  was  reached,  the  vicinists  not  being 
more  numerous  than  10^  of  the  entire  number. 
The  same  mutation  had  been  observed  a  year 
earlier  in  the  same  nursery  in  a  lot  of  Saponaria 
calahrica.  The  seeds  of  this  dwarf  repeated  the 
variety  in  the  next  generation,  but  in  the  third 
none  were   observed.      Then  the  variety  was 


Mutations  in  Horticulture  613 

thought  to  be  lost,  and  the  culture  was  given  up, 
as  the  Mendelian  law  of  the  splitting  of  varietal 
hybrids  was  not  known.  According  to  our  pres- 
ent knowledge  we  might  expect  the  atavistic  de- 
scendants of  the  first  dwarf  to  be  hybrids,  and 
to  be  liable  to  split  in  their  progeny  into  one- 
fourth  dwarfs  and  three-fourths  normal  speci- 
mens. From  this  it  is  obvious  that  the  dwarfs 
would  have  appeared  a  second  time  if  the  strain 
had  been  continued  by  means  of  the  seeds  of  the 
vicinistic  progeny. 

In  order  to  avoid  a  return  to  this  phase  of  the 
question,  another  use  of  the  vicinists  should  at 
once  be  pointed  out.  It  is  the  possibility  of  in- 
creasing the  yield  of  the  new  variety.  If  space 
admits  of  sowing  the  seeds  of  the  vicinists,  a 
quarter  of  the  progeny  may  be  expected  to  come 
true  to  the  new  type,  and  if  they  were  partly 
pollinated  by  the  dwarfs,  even  a  larger  number 
would  do  so.  Hence  it  should  be  made  a  rule  to 
sow  these  seeds  also,  at  least  when  those  of  the 
true  representatives  of  the  novelty  do  not  give 
seed  enough  for  a  rapid  multiplication. 

Other  dwarfs  are  recorded  to  have  sprung 
from  species  in  the  same  sudden  and  unexpected 
manner,  as  for  instance  Ageratum  coeruleum  of 
the  same  nursery,  further  Clematis  Viticella 
nana  and  Acer  campestre  nanum.  Primus  Ma- 
haleb    nana   was    discovered    in    1828    in    one 


614  Mutations 

specimen  near  Orleans  by  Mme  LeBrun  in  a 
large  culture  of  Mahaleb.  Lonicera  tatar- 
ica  nana  appeared  in  1825  at  Fontenay-aux- 
Roses.  A  tall  variety  of  the  strawberry  is 
called  "  Giant  of  Zuidwijk  "  and  originated  at 
Boskoop  in  Holland  in  the  nursery  of  Mr.  van 
de  Water,  in  a  lot  of  seedlings  of  the  ordinary 
strawberry.  It  was  very  large,  but  produced 
few  runners,  and  was  propagated  with  much  dif- 
ficulty, for  after  six  years  only  15  plants  were 
available.  It  proved  to  be  a  late  variety  with 
abundant  large  fruit,  and  was  sold  at  a  high 
price.  For  a  long  time  it  was  prominent  in 
cultures  in  Holland  only. 

Varieties  without  prickles  are  known  to  have 
originated  all  of  a  sudden  in  sundry  cases. 
Gleditschia  sinensis,  introduced  in  1774  from 
China,  gave  two  seedlings  without  spines  in  the 
year  1823,  in  the  nursery  of  Caumzet.  It  is 
curious  in  being  one  of  the  rare  instances  where 
a  simultaneous  mutation  in  two  specimens  is 
acknowledged,  because  as  a  rule,  such  records 
comply  with  the  prevailing,  though  inexact,  be- 
lief that  horticultural  mutations  always  appear 
in  single  individuals. 

Prom  Korshinsky's  survey  of  varieties  with 
cut  leaves  or  laciniate  forms  the  following  cases 
may  be  quoted.  In  the  year  1830  a  nurseryman 
named  Jacques  had  sown  a  large  lot  of  elms. 


Mutations  in  Horticulture  615 

Ulmus  pedunculata.  One  of  the  seedlings  had 
cut  leaves.  He  multiplied  it  by  grafting  and 
gave  it  to  the  trade  under  the  name  of  U. 
pedunculata  urticaefolia.  It  has  since  been 
lost. 

Laciniate  alders  seem  to  have  been  produced 
by  mutation  at  sundry  times.  Mirbel  says  that 
the  Alnus  glutinosa  laciniata  is  found  wild  in 
Normandy  and  in  the  forests  of  Montmorency 
near  Paris.  A  similar  variety  has  been  met 
with  in  a  nursery  near  Orleans  in  the  year  1855. 
In  connection  with  this  discovery  some  discus- 
sion has  arisen  concerning  the  question  whether 
it  was  probable  that  the  Orleans  strain  was  a 
new  mutation,  or  derived  in  some  way  from  the 
trees  cited  by  Mirbel.  Of  course,  as  always  in 
such  cases,  any  doubt,  once  pronounced,  affects 
the  importance  of  the  observation  for  all  time, 
since  it  is  impossible  to  gather  sufficient  his- 
torical evidence  to  fully  decide  the  point.  The 
same  variety  had  appeared  under  similar  cir- 
cumstances in  a  nursery  at  Lyons  previously 
(1812). 

Laciniated  maples  are  said  to  be  of  relatively 
frequent  occurrence  in  nurseries,  among  seed- 
lings of  the  typical  species.  Loudon  says  that 
once  100  laciniated  seedlings  were  seen  to  orig- 
inate from  seed  of  some  normal  trees.  But  in 
this  case  it  is  rather  probable  that  the  presumed 


616  Mutations  ^ 

normal  parents  were  in  reality  hybrids  between 
the  type  and  the  laciniated  form,  and  simply 
split  according  to  Mendel's  law.  This  hy- 
pothesis is  partly  founded  on  general  consider- 
ations and  partly  on  experiments  made  by  my- 
self with  the  cut-leaved  celandine,  previously 
alluded  to,  which  I  crossed  with  the  type.  The 
hybrids  repeated  the  features  of  the  species  and 
showed  no  signs  of  their  internal  hybrid  con- 
stitution. But  the  following  year  one-fourth 
of  their  progeny  returned  to  the  cut-leaved 
form.  If  the  same  thing  has  taken  place  in  the 
case  of  Loudon's  maples,  but  without  their 
hybrid  origin  being  known,  the  result  would 
have  been  precisely  what  he  observed. 

Broussonetia  papyrifera  dissecta  originated 
about  1830  at  Lyons,  and  a  second  time  in  1866 
at  Fontenay-aux-Eoses.  The  cut-leaved  hazel- 
nuts, birches,  beeches  and  others  have  mostly 
been  found  in  the  wild  state,  as  I  have  already 
pointed  out  in  a  previous  lecture.  A  similar 
variety  of  the  elder,  Samhucus  nigra  laciniata, 
and  its  near  ally,  Samhucus  racemosa  laciniata, 
are  often  to  be  seen  in  our  gardens.  They  have 
been  on  record  since  1886  and  come  true  from 
seed,  but  their  exact  origin  seems  to  have  been 
forgotten.  Cut-leaved  walnuts  have  been  known 
since  1812;  they  come  true  from  seed,  but  are 
extremely  liable  to  vicinism,  a  nuisance  which  is 


Mutations  in  Horticulture  617 

ascribed  by  some  authors  to  the  fact  that  often 
on  the  same  tree  the  male  catkins  flower  and  fall 
otf  several  weeks  before  the  ripening  of  the 
pistils  of  the  other  form  of  flowers. 

Weeping  varieties  afford  similar  instances. 
Sophora  japonica  pendula  originated  about 
1850,  and  Gleditschia  triacanthos  pendula  some 
time  later  in  a  nursery  at  Chateau-Thierry 
(Ai^ne,  France).  In  the  year  1821  the  bird's 
cherry,  or  Prunus  Padus,  produced  a  weeping 
variety,  and  in  1847  the  same  mutation  was  ob- 
served for  the  allied  Primus  Mahaleh.  Numer- 
ous other  instances  of  the  sudden  origin  of 
weeping  trees,  both  of  conifers  and  of  others, 
have  been  brought  together  in  Korshinsky's 
paper.  This  striking  type  of  variation  includes 
perhaps  the  best  examples  of  the  whole  his- 
torical evidence.  As  a  rule  they  appear  in  large 
sowings,  only  one,  or  only  a  few  at  a  time.  Many 
of  them  have  not  been  observed  during  their 
youth,  but  only  after  having  been  planted  out 
in  parks  and  forests,  since  the  weeping  charac- 
ters show  only  after  several  years. 

The  monophyllous  bastard-acacia  originated 
in  the  same  way.  Its  peculiarities  will  be  dealt 
with  on  another  occasion,  but  the  circumstances 
of  its  birth  may  as  well  be  given  here.  In  1855 
in  the  nursery  of  Deniau,  at  Brain-sur-PAu- 
thion  (Maine  et  Loire),  it  appeared  in  a  lot  of 


618  Mutations 

seedlings  of  the  typical  species  in  a  single  in- 
dividual. This  was  transplanted  into  the  Jar- 
din  des  Plantes  at  Paris,  where  it  flowered  and 
bore  seeds  in  1865.  It  must  have  been  partly 
pollinated  by  the  surrounding  normal  repre- 
sentatives of  the  species,  since  the  seeds  yielded 
only  one-fourth  of  true  offspring.  This  propor- 
tion, however,  has  varied  in  succeeding  years. 
Briot  remarks  that  the  monophyllous  bastard- 
acacia  is  liable  to  petaloid  alterations  of  its 
stamens,  which  deficiency  may  encroach  upon 
its  fertility  and  accordingly  upon  the  purity  of 
its  offspring. 

Broom-like  varieties  often  occur  among  trees, 
and  some  are  known  for  their  very  striking  re- 
versions by  buds,  as  we  have  seen  on  a  previous 
occasion.  They  are  ordinarily  called  pyramidal 
or  fastigiate  forms,  and  as  far  as  their  history 
goes,  they  arise  suddenly  in  large  sowings 
of  the  normal  species.  The  fastigiate  birch  was 
produced  in  this  way  by  Baumann,  the  Abies 
concolor  fastigiata  by  Thibault  and  Keteleer  at 
Paris,  the  pyramidal  cedar  by  Paillat,  the  analo- 
gous form  of  W ellingtonia  by  Otin.  Other  in- 
stances could  easily  be  added,  though  of  course 
some  of  the  most  highly  prized  broom-like  trees 
are  so  old  that  nothing  is  known  about  their 
origin.  This,  for  instance,  is  the  case  with  the 
pyramidal  yew-tree,  Taxus  haccata  fastigiata. 


Mutations  in  Horticulture  619 

Others  have  been  found  wild,  as  already  men- 
tioned in  a  former  lecture. 

An  analogous  case  is  afforded  by  the  purple- 
leaved  plums,  of  which  the  most  known  form  is 
Prunus  Pissardi.  It  is  said  to  be  a  purple  va- 
riety of  Prunus  cerasifera,  and  was  introduced 
at  the  close  of  the  seventies  from  Persia,  where 
it  is  said  to  have  been  found  in  Tabris.  A  simi- 
lar variety  arose  independently  and  unex- 
pectedly in  the  nursery  of  Spath,  near  Berlin, 
about  1880,  but  it  seems  to  differ  in  some  minor 
points  from  the  Persian  prototype. 

A  white  variety  of  Cyclamen  vernum  made  its 
appearance  in  the  year  1836  in  Holland.  A  sin- 
gle individual  was  observed  for  the  first  time 
among  a  large  lot  of  seedlings,  in  a  nursery  near 
Haarlem.  It  yielded  a  satisfactory  amount  of 
seed,  and  the  progeny  was  true  to  the  new  type. 
Such  plants  propagate  slowly,  and  it  was  only 
twenty-seven  years  later  (1863)  that  the  bulbs 
were  offered  for  sale  bv  the  Haarlem  firm  of 
Krelage  &  Son.  The  price  of  each  bulb  was 
$5.00  in  that  year,  but  soon  afterwards  was  re- 
duced to  $1.00  each,  which  was  about  thrice  the 
ordinary  price  of  the  red  variety. 

The  firm  of  Messrs.  Krelage  &  Son  has 
brought  into  commerce  a  wide  range  of  new 
bulb-varieties,  all  due  to  occasional  mutations, 
some  by  seed  and  others  by  buds,  or  to  the  acci- 


620  Mutations 

dental  transference  of  new  qualities  into  the 
already  existing  varieties  by  cross-pollination 
through  the  agency  of  insects.  Instead  of  giv- 
ing long  lists  of  these  novelties,  I  may  cite  the 
black  tulips,  which  cost  during  the  first  few 
years  of  their  introduction  about  $25.00  apiece. 

Horticultural  mutations  are  as  a  rule  very 
rare,  especially  in  genera  or  species  which  have 
not  yet  been  brought  to  a  high  degree  of  varia- 
bility. In  these  the  wide  range  of  varieties  and 
the  large  scale  in  which  they  are  multiplied  of 
course  give  a  greater  chance  for  new  varieties. 
But  then  the  possibilities  of  crossing  are  like- 
wise much  larger,  and  apparent  changes  due  to 
this  cause  may  easily  be  taken  for  original  mu- 
tations. 

The  rarity  of  the  mutations  is  often  proved 
by  the  lapse  of  time  between  the  introduction 
of  a  species  and  its  first  sport.  Some  instances 
may  be  given.  They  afford  a  proof  of  the  length 
of  the  period  during  which  the  species  remained 
unaltered,  although  some  of  these  alterations 
may  be  due  to  a  cross  with  an  allied  form. 
Erythrina  Crista-galli  was  introduced  about 
1770,  and  produced  its  first  sport  in  1884,  after 
more  than  a  century  of  cultivation.  Begonia 
semperflorens  has  been  cultivated  since  1829, 
and  for  half  a  century  before  it  commenced 
sporting.     The  same  length  of  time  has  elapsed 


Mutations  in  Horticulture  621 

between  the  first  culture  and  the  first  variation 
of  Crambe  maritima.  Other  cases  are  on  rec- 
ord in  which  the  variability  exhibited  itself 
much  sooner,  perhaps  within  a  few  years  after 
the  original  discovery  of  the  species.  But  such 
instances  seem,  as  a  rule,  to  be  subject  to  doubt 
as  to  the  concurrence  of  hybridization.  So  for 
instance  the  Iris  lortetii,  introduced  in  the  year 
1895  from  the  Lebanon,  which  produced  a  white 
variety  from  its  very  first  seeds.  If  by  chance 
the  introduced  plants  were  natural  hybrids  be- 
tween the  species  and  the  white  variety,  this  ap- 
parent and  rather  improbable  mutation  would 
find  a  very  simple  explanation.  The  length  of 
the  period  preceding  the  first  signs  of  variability 
is  largely,  of  course,  due  to  divergent  methods 
of  culture.  Such  species  as  Erythrina,  which 
are  perennial  and  only  sown  on  a  small  scale, 
should  not  be  expected  to  show  varieties  very 
soon.  Annual  species,  which  are  cultivated 
yearly  in  thousands  or  even  hundreds  of  thou- 
sands of  individuals,  have  a  much  better  chance. 
Perhaps  the  observed  differences  are  largely 
due  to  this  cause. 

Monstrosities  have,  from  time  to  time,  given 
rise  to  cultivated  races.  The  cockscomb  or 
Celosia  is  one  of  the  most  notorious  instances. 
Cauliflowers,  turnips  and  varieties  of  cabbages 
are  recorded  by  De  Candolle  to  have  arisen  in 


622  Mutations 

culture,  more  than  a  century  ago,  as  isolated 
monstrous  individuals.  They  come  true  from 
seed,  but  show  deviations  from  time  to  time 
which  seem  to  be  intimately  linked  with  their 
abnormal  characters.  Apetalous  flowers  may 
be  considered  as  another  form  of  monstrosity, 
and  in  Salpiglossis  sinuata  such  a  variety  with- 
out a  corolla  made  its  appearance  in  the  year 
1892  in  the  nursery  of  Vilmorin.  It  appeared 
suddenly,  yielded  a  good  crop  of  seed  and 
was  constant  from  the  outset,  without  any  sign 
of  vicinism  or  impurity. 

In  several  cases  the  origin  of  a  variety  is  ob- 
scure, while  the  subsequent  historical  evidence 
is  such  as  to  make  an  original  sudden  appear- 
ance quite  probable.  Although  these  instances 
otfer  but  indirect  evidence,  and  will  sooner  or 
later  lose  their  importance,  it  seems  desirable 
to  lay  some  stress  on  them  here,  because  most  of 
these  cases  are  very  obvious  and  more  striking 
than  purely  historical  facts.  Sterile  varieties 
belong  to  this  heading.  Sometimes  they  bear 
fruit  without  kernels,  sometimes  flowers  with- 
out sexual  organs,  or  even  no  flowers  at  all.  In- 
stances have  been  given  in  the  lecture  on 
retrograde  varieties;  they  are  ordinarily  as- 
sumed to  have  originated  by  a  leap,  because  it  is 
not  quite  clear  how  a  loss  of  the  capacity  for  the 
formation  of  seeds  could  have  been  slowlv  accu- 


Mutations  in  Horticulture  623 

mulated  in  preceding  generations.  An  interest- 
ing case  is  afforded  by  a  sterile  variety  of  corn, 
which  originated  some  time  ago  in  my  own  pedi- 
gree-cultures made  for  another  purpose,  and 
which  had  begun  with  an  ear  of  1886.  The  first 
generation  from  the  original  seeds  showed  noth- 
ing particular,  but  the  second  at  once  produced 
quite  a  number  of  sterile  plants.  The  sterility 
was  caused  by  the  total  lack  of  branches,  includ- 
ing those  bearing  the  pistillate  flowers.  The 
terminal  spikes  themselves  were  reduced  to 
naked  spindles,  without  branches,  without  flow- 
ers and  even  almost  without  bracts. 

In  some  individuals,  however,  this  negative 
character  was  seen  to  give  way  at  the  tip,  show- 
ing a  few  small  naked  branches.  Of  course  it 
was  impossible  to  propagate  this  curious  form, 
but  my  observations  showed  that  it  sprang  into 
existence  from  known  ancestors  by  a  single  step 
or  sudden  leap.  This  leap,  however,  was  not 
confined  to  a  single  specimen;  on  the  contrary 
it  affected  40  plants  out  of  a  culture  of  340 
individuals.  The  same  phenomenon  was  re- 
peated from  the  seeds  of  the  normal  plants  in 
the  following  year,  but  afterwards  the  mon- 
strosity disappeared. 

The  Italian  poplar  affords  another  instance. 
It  is  considered  bv  some  authors  as  a  distinct 
species,   Popidus   italica,   and   by   others   as  a 


624  Mutations 

broom-like  variety  of  the  Populus  nigra,  from 
which  it  is  distinguished  by  its  erect  branches 
and  other  characters  of  minor  importance.  It 
is  often  called  the  pyramidal  or  fastigiate 
poplar.  Its  origin  is  absolutely  unknown  and 
it  occurs  only  in  the  cultivated  state.  In  Italy 
it  seems  to  have  been  cultivated  from  the 
earliest  historical  times,  but  it  was  not  intro- 
duced into  other  countries  till  the  eighteenth 
century.  In  1749  it  was  brought  into  France, 
and  in  1758  into  England,  and  to-day  it 
may  be  seen  along  roads  throughout  cen- 
tral Europe  and  in  a  large  part  of  Asia.  But 
the  most  curious  fact  is  that  it  is  only  observed 
in  staminate  specimens ;  pistillate  trees  have  not 
been  found,  although  often  sought  for.  This 
circumstance  makes  it  very  probable  that  the 
origin  of  the  broom-like  poplar  was  a  sudden 
mutation,  producing  only  one  individual.  This 
being  staminate,  it  has  been  propagated  ex- 
clusively by  cuttings.  It  is  to  be  admitted, 
however,  that  no  material  evidence  is  at  hand 
to  prove  that  it  is  not  an  original  wild  species, 
the  pistillate  form  of  which  has  been  lost  by 
vegetative  multiplication.  One  form  only  of 
many  dioecious  plants  is  to  be  found  in  cultiva- 
tion, as  for  instance  some  South  American 
species  of  Ribes. 

Total  lack  of  historical  evidence  concerning 


Mutations  in  Horticulture  625 

the  origin  of  a  variety  has  sometimes  been  con- 
sidered as  sufficient  proof  of  a  sudden  origin. 
The  best  known  instance  is  that  of  the  renowned 
cactus-dahlia  with  its  recurved  instead  of  in- 
curved ray-florets.  It  was  introduced  from 
Mexico  into  the  Netherlands  by  Van  den  Berg  of 
Jutphaas,  under  the  following  remarkable  cir- 
cumstances. In  the  autumn  of  1872  one  of  his 
friends  had  sent  him  a  small  case,  containing 
seeds,  bulbs  and  roots  from  Mexico.  From 
one  of  these  roots  a  Dahlia  shoot  developed. 
It  was  cultivated  with  great  care  and  bloomed 
next  year.  It  surprised  all  who  saw  it  by 
the  unexpected  peculiarity  of  its  large  rich 
crimson  flowers,  the  rays  of  which  were  re- 
versed tubular.  The  margins  of  the  narrow 
rays  were  curved  backwards,  showing  the  bright 
color  of  the  upper  surface.  It  was  a  very 
showy  novelty,  rapidly  multiplied  by  cuttings, 
and  was  soon  introduced  into  commerce.  It  has 
since  been  crossed  with  nearly  all  other  avail- 
able varieties  of  the  Dahlia,  giving  a  large  and 
rich  group  of  forms,  bound  together  by  the 
curious  curling  of  the  petals.  It  has  never  been 
observed  to  grow  in  Mexico,  either  wild  or  in 
gardens,  and  thus  the  introduced  individual  has 
come  to  be  considered  as  the  first  of  its  race. 

I  have  already  mentioned  that  the  rapid  pro- 
duction of  large  numbers  of  new  varieties,  by 


626  Mutations 

means  of  the  crossing  of  the  offspring  of  a 
single  mutant  with  previously  existing  sorts,  is 
a  very  common  feature  in  horticultural  prac- 
tice. It  warns  us  that  only  a  small  part  of  the 
novelties  introduced  yearly  are  due  to  real  mu- 
tations. Further  instances  of  novelties  with 
such  a  common  origin  are  the  purple-leaved 
dahlias,  the  gooseberries  without  prickles,  the 
double  petunias,  erect  gloxinias  and  many 
others.  Accumulation  of  characters,  acquired 
in  different  races  of  a  species,  may  easily  be 
effected  in  this  way ;  in  fact  it  is  one  of  the  im- 
portant factors  in  the  breeding  of  horticultural 
novelties. 

I  have  alluded  more  than  once  in  this  lecture 
to  the  question,  whether  it  is  probable  that  mu- 
tations occur  in  one  individual  or  in  more. 
The  common  belief  among  horticulturists  is 
that,  as  a  rule,  they  appear  in  a  single  plant. 
This  belief  is  so  widespread  that  whenever  a 
novelty  is  seen  for  the  first  time  in  two  or  more 
specimens  it  is  at  once  suggested  that  it  might 
have  originated  and  been  overlooked  in  a  previ- 
ous generation.  Not  caring  to  confess  a  lack 
of  close  observation,  the  number  of  mutants 
in  such  cases  is  usually  kept  secret.  At  least 
this  statement  has  been  made  to  me  by  some  of 
the  horticulturists  at  Erfurt,  whom  I  visited 
some  years  ago  in  order  to  learn  as  much  as 


Mutations  in  Horticulture  627 

possible  about  the  methods  of  production  of 
their  novelties.  Hence  it  is  simply  impossible 
to  decide  the  question  on  the  basis  of  the  ex- 
perience of  the  breeders.  Even  in  the  case  of  the 
same  novelty  arising  in  sundry  varieties  of  the 
same  species,  the  question  as  to  common  origin, 
by  means  of  crossing,  is  often  hard  to  decide, 
as  for  instance  in  moss-roses  and  nectarines. 
On  the  other  hand,  instances  are  on  record 
where  the  same  novelty  has  appeared  at  differ- 
ent times,  often  at  long  intervals.  Such  is  the 
case  with  the  butterfly-cyclamen,  a  form  with 
wide-spreading  petals  which  originated  in 
Martinis  nursery  in  England.  The  first  time  it 
was  seen  it  was  thought  to  be  of  no  value,  and 
was  thrown  away,  but  when  appearing  for  a 
second  time  it  was  multiplied  and  eventually 
placed  on  the  market.  Other  varieties  of  Cycla- 
men, as  for  instance  the  crested  forms,  are  also 
known  to  have  originated  repeatedly. 

In  concluding  this  series  of  examples  of  hor- 
ticultural mutations,  I  might  mention  two 
cases,  which  have  occurred  in  my  own  experi- 
mental garden.  The  first  refers  to  a  tubular 
dahlia.  It  has  ray-florets,  the  ligules  of  which 
have  their  margins  grown  together  so  as  to 
form  tubes,  with  the  outer  surface  correspond- 
ing to  the  pale  under-surface  of  the  corolla. 

This  novelty  originated  in  a  single  plant  in  a 


628  Mutations 

culture  from  the  seed  of  the  dwarf  variety 
'  ^  Jules  Chretien. ' '  The  seeds  were  taken  from 
introduced  plants  in  my  garden,  and  as  the 
sport  has  no  ornamental  value  it  is  uncertain 
whether  this  was  the  first  instance  or  whether 
it  had  previously  occurred  in  the  nursery  at 
Lyons,  from  whence  the  bulbs  were  secured. 
Afterwards  it  proved  true  from  seed,  but  was 
very  variable,  exhibiting  rather  the  features  of 
an  ever-sporting  variety. 

Another  novelty  was  seen  the  first  time  in 
several  individuals.  It  was  a  pink  sport  of  the 
European  cranesbill.  Geranium  pratense.  It 
arose  quite  unexpectedly  in  the  summer  of  1902 
from  a  striped  variety  of  the  blue  species.  It 
was  seen  in  seven  specimens  out  of  a  lot  of  about 
a  hundred  plants.  This  strain  was  introduced 
into  my  garden  in  1897,  when  I  bought  two 
plants  under  the  name  of  Geranium  pratense 
album,  which  however  proved  to  belong  to  the 
striped  variety.  From  their  seeds  I  sowed  in 
1898  a  first  generation,  of  which  a  hundred 
plants  flowered  the  next  year,  and  from  their 
seeds  I  sowed  in  1900  the  lot  which  produced 
the  sport.  Neither  the  introduced  plants  nor 
their  offspring  had  exhibited  the  least  sign  of  a 
color-variation,  besides  the  blue  and  white 
stripes.  Hence  it  is  very  probable  that  my  nov- 
elty was  a  true  first  mutation,  the  more  prob- 


Mutations  in  Horticulture  629 

ably  so  since  a  pink  variety  would  without  doubt 
have  a  certain  horticultural  value  and  would 
have  been  preserved  if  it  had  occurred.  But  as 
far  as  I  have  been  able  to  ascertain,  it  is  as  yet 
unknown,  nor  has  it  been  described  until  to-day. 
Summing  up  the  results  of  this  long,  though 
very  incomplete,  list  of  horticultural  novelties 
with  a  more  or  less  well-known  origin,  we  see 
that  sudden  appearances  are  the  rule.  Having 
once  sprung  into  existence  the  new  varieties  are 
ordinarily  constant,  except  as  affected  by 
vicinism.  Details  concerning  the  process  are 
mostly  unavailable  or  at  least  are  of  very  doubt- 
ful value.  And  to  this  it  should  be  added  that 
really  progressive  mutations  have  hardly  been 
observed  in  horticulture.  Hence  the  theoretical 
value  of  the  facts  is  far  less  than  might  have 
been  expected. 


Lecture  XXII 


SYSTEMATIC   ATAVISM 


The  steady  cooperation  of  progression  and  re- 
trogression is  one  of  the  important  principles 
of  organic  evolution.  I  have  dwelt  upon  this 
point  more  than  once  in  previous  lectures.  I 
have  tried  to  show  that  both  in  the  more  im- 
portant lines  of  the  general  pedigree  of  the 
vegetable  kingdom,  and  in  the  numerous  lateral 
branches  ending  in  the  genera  and  species  with- 
in the  families,  progression  and  retrogression 
are  nearly  always  at  work  together.  Your  at- 
tention has  been  directed  to  the  monocotyledons 
as  an  example,  where  retrogression  is  every- 
where so  active  that  it  can  almost  be  said  to  be 
the  prevailing  movement.  Reduction  in  the  veg- 
etative and  generative  organs,  in  the  anatomical 
structure  and  growth  of  the  stems,  and  in  sun- 
dry other  ways  is  the  method  by  which  the 
monocotyledons  have  originated  as  a  group 
from  their  supposed  ancestors  among  the  lower 
dicotyledonous  families.  Retrogression  is  the 
leading  idea  in  the  larger  families  of  the  group, 

630 


Systematic  Atavism  631 

as  for  instance  in  the  aroids  and  the  grasses. 
Retrograde  evolution  is  also  typical  in  the  high- 
est and  most  highly  differentiated  family  of  the 
monocotyledons,  the  orchids,  which  have  but 
one  or  two  stamens.  In  the  second  place  I  have 
had  occasion  more  than  once  to  assert  that  retro- 
gression, though  seemingly  consisting  in  the 
disappearance  of  some  quality,  need  not,  as  a 
rule,  be  considered  as  a  complete  loss.  Quite  on 
the  contrary,  it  is  very  probable  that  real  losses 
are  extremely  rare,  if  not  wholly  lacking.  Ordi- 
narily the  loss  is  only  apparent,  the  capacity 
becomes  inactive  only,  but  is  not  destroyed.  The 
character  has  become  latent,  as  it  is  commonly 
stated,  and  therefore  may  return  to  activity  and 
to  the  full  display  of  its  peculiarity,  whenever 
occasion  offers. 

Such  a  return  to  activity  was  formerly  called 
atavism.  But  as  we  have  seen,  when  dealing 
with  the  phenomena  of  latency  at  large,  sundry 
eases  of  latency  are  to  be  distinguished,  in  order 
to  get  a  clear  insight  into  these  difficult  proc- 
esses. 

So  it  is  with  atavism,  too.  If  any  plant  re- 
verts to  a  known  ancestor,  we  have  a  positive 
and  simple  case.  But  ancestors  with  alternate 
specific  marks  are  as  a  rule  neither  historically 
nor  experimentally  manifest.  They  are  only 
reputed  to  be  such,  and  the  presumption  rests 


632  Mutations 

upon  the  systematic  affinity  between  the  deriva- 
tive species  and  its  nearest  probable  allies. 
Such  reversions  are  now  to  be  examined  at  some 
length  and  may  be  adequately  treated  under  the 
head  of  systematic  atavism.  To  this  form  of 
atavism  pertain,  on  the  basis  of  our  definition, 
those  phenomena  by  which  species  assume  one 
or  more  characters  of  allies,  from  which  they 
are  understood  to  have  descended  by  the  loss  of 
the  character  under  discussion.  The  phenom- 
ena themselves  consist  in  the  production  of 
anomalies  and  varieties,  and  as  the  genetic 
relation  of  the  latter  is  often  hardly  beyond 
doubt,  the  anomalies  seem  to  afford  the  best  in- 
stances for  the  study  of  systematic  atavism. 
This  study  has  for  its  chief  aim  the  demonstra- 
tion of  the  presence  of  the  latent  characters,  and 
to  show  that  they  return  to  activity  suddenly 
and  not  by  a  slow  and  gradual  recovery  of  the 
former  features.  It  supports  the  assertion 
that  the  visible  elementary  characters  are  es- 
sentially an  external  display  of  qualities  carried 
by  the  bearers  of  heredity,  and  that  these 
bearers  are  separate  entities,  which  may  be 
mingled  together,  but  are  not  fused  into  a 
chaotic  primitive  life-substance.  Systematic 
atavism  by  this  means  leads  us  to  a  closer  ex- 
amination of  the  internal  and  concealed  causes, 
which  rule  the  affinities   and  divergencies   of 


Systematic  Atavism  633 

allied  species.  It  brings  before  us,  and  empha- 
sizes the  importance  of  the  conception  of  the 
so-called  unit-characters. 

The  primrose  will  serve  as  an  example.  In 
the  second  lecture  we  have  seen  that  the  old 
species  of  Linnaeus,  the  Prmiida  veris,  was 
split  up  by  Jacquin  into  three  smaller  ones, 
which  are  called  P.  officinalis,  P.  elatior  and  P. 
acaulis.  From  this  systematic  treatment  we 
can  infer  that  these  three  forms  are  assumed  to 
be  derived  from  a  common  ancestor.  Now  two 
of  them  bear  their  flowers  in  bracted  whorls, 
condensed  into  umbels  at  the  summits  of  a  scape. 
The  scapes  themselves  are  inserted  in  the  axils 
of  the  basal  leaves,  and  produce  the  flowers 
above  them.  In  the  third  species.  Primula 
acaulis,  this  scape  is  lacking  and  the  flowers  are 
inserted  singly  in  the  axils  on  long  slender 
stalks.  For  this  reason  the  species  is  called 
acaulescent,  indicating  that  it  has  no  other 
stem  than  the  subterranean  rootstock.  But  on 
closer  inspection  we  observe  that  the  flower- 
stalks  are  combined  into  little  groups,  each 
group  occupying  the  axil  of  one  of  the  basal 
leaves.  This  fact  at  once  points  to  an  analogy 
with  the  umbellate  allies,  and  induces  us  to  ex- 
amine the  insertion  of  the  flowers  more  crit- 
ically. In  doing  so  we  find  that  they  are  united 
at  their  base  so  as  to  constitute  a  sessile  umbel. 


634  Mutations 

The  scapes  are  not  absolutely  lacking,  but  only 
reduced  to  almost  invisible  rudiments. 

Belying  upon  this  conclusion  we  infer  that  all 
of  the  three  elementary  species  have  umbels, 
some  pedunculate  and  the  others  not.  On  this 
point  they  agree  with  the  majority  of  the  allied 
species  in  the  genus  and  in  other  genera,  as  for 
instance  in  Androsace.  Hence  the  conclusion 
that  the  common  ancestors  were  perennial 
plants  with  a  rootstock  bearing  their  flowers 
in  umbels  or  whorls  on  scapes.  Lacking  in  the 
Primula  veris,  these  scapes  must  obviously  have 
been  lost  at  the  time  of  the  evolution  of  this 
form. 

Proceeding  on  this  line  of  speculation  we  at 
once  see  that  a  very  adequate  opportunity  for 
systematic  atavism  is  offered  here.  According 
to  our  general  conception  the  apparent  loss  of  a 
scape  is  no  proof  of  a  corresponding  internal 
loss,  but  might  as  well  be  caused  simply  by 
the  reduction  of  the  scape-growing  capacity  to 
a  latent  or  inactive  state.  It  might  be  awak- 
ened afterwards  by  some  unknown  agency,  and 
return  to  activity. 

Now  this  is  exactly  what  happens  from  time 
to  time.  In  Holland  the  acaulescent  primrose 
is  quite  a  common  plant,  filling  the  woods  in  the 
spring  with  thousands  of  clusters  of  bright  yel- 
low flowers.     It  is  a  very  uniform  type,  but  in 


Systematic  Atavism  635 

some  years  it  is  seen  to  return  to  atavistic  con- 
ditions in  some  rare  individuals.  More  than 
once  I  have  observed  such  cases  myself,  and 
found  that  the  variation  is  only  a  partial  one, 
producing  one  or  rarely  two  umbels  on  the  same 
plant,  and  liable  to  fail  of  repetition  when  tlie 
varying  specimens  are  transplanted  into  the 
garden  for  further  observation.  But  the  fact 
remains  that  scapes  occur.  The  scapes  them- 
selves are  of  varying  length,  often  very  short, 
and  seldom  long,  and  their  umbels  display  the 
involucre  of  bracts  in  a  manner  quite  analogous 
to  that  of  the  Primula  officinalis  and  P.  elatior. 
To  my  mind  this  curious  anomaly  strongly  sup- 
ports the  view  of  the  latent  condition  of  the 
scape  in  the  acaulescent  species,  and  that  such  a 
dormant  character  must  be  due  to  a  descent 
from  ancestors  with  active  scapes,  seems  to  be  in 
no  need  of  further  reiteration.  Returning  to. 
activity  the  scapes  at  once  show  a  full  develop- 
ment, in  no  way  inferior  to  that  of  the  allied 
forms,  and  only  unstable  in  respect  to  their 
length. 

A  second  example  is  afforded  by  the  bracts 
of  the  crucifers.  This  group  is  easily  distin- 
guished by  its  cruciform  petals  and  the  group- 
ing of  the  flowers  into  long  racemes.  In  other 
families  each  flower  of  such  an  inflorescence 
would  be  subtended  by  a  bract,  according  to  the 


636  Mutations 

general  rule  that  in  the  higher  plants  side 
branches  are  situated  in  the  axils  of  leaves. 
Bracts  are  reduced  leaves,  but  the  spikes  of  the 
cruciferous  plants  are  generally  devoid  of 
them.  The  flower-stalks,  with  naked  bases, 
seem  to  arise  from  the  common  axis  at  indefinite 
points. 

Hence  the  inference  that  crucifers  are  an  ex- 
ception to  a  general  rule,  and  that  they  must 
have  originated  from  other  types  which  did 
comply  with  this  rule,  and  accordingly  were  in 
the  possession  of  floral  bracts.  Or,  in  other 
words,  that  the  bracts  must  have  been  lost  dur- 
ing the  original  evolution  of  the  whole  family. 
This  conclusion  being  accepted,  the  accidental 
re-apparition  of  bracts  within  the  family  must 
be  considered  as  a  case  of  systematic  atavism, 
quite  analogous  to  the  re-appearance  of  the 
scapes  in  the  acaulescent  primrose.  The  sys- 
tematic importance  of  this  phenomenon,  how- 
ever, is  far  greater  than  in  the  first  case,  in 
which  we  had  only  to  deal  with  a  specific  char- 
acter, while  the  abolition  of  the  bracts  has  be- 
come a  feature  of  a  whole  family. 

This  reversion  is  observed  to  take  place  ac- 
cording to  two  widely  different  principles.  On 
one  hand,  bracts  may  be  met  with  in  a  few 
stray  species,  assuming  the  rank  of  a  specific 
character.     On  the  other  hand  they  may  be  seen 


Systematic  Atavism  637 

to  occur  as  an  anomaly,  incompletely  developed, 
often  very  rare  and  with  all  the  appearance  of 
an  accidental  variation,  but  sometimes  so  com- 
mon as  to  seem  nearly  normal. 

Coming  now  to  particular  instances,  we  may 
turn  our  attention  in  the  first  place  to  the  genus 
Sisymbrium.  This  is  a  group  of  about  50  species, 
of  wide  geographic  distribution,  among  which 
the  hedge  mustard  (S.  offlcinalis)  is  perhaps  the 
most  common  of  weeds.  Two  species  are  re- 
puted to  have  bracts,  Sisymbrium  hirsutum  and 
S.  supiniim.  Each  flower-stalk  of  their  long 
racemes  is  situated  in  the  axil  of  such  a  bract, 
and  the  peculiaritj^  is  quite  a  natural  one,  corre- 
sponding exactly  to  what  is  seen  in  the  inflor- 
escence of  other  families.  Besides  the  Sisym- 
brium some  six  other  genera  afford  similar 
structures. 

Erucastrum  pollichii  has  been  already  allud- 
ed to  in  a  former  lecture  when  dealing  with  the 
same  problem  from  another  point  of  view.  As 
previously  stated,  it  is  one  of  the  most  manifest 
and  most  easily  accessible  examples  of  a  latent 
character  becoming  active  through  systematic 
atavism.  In  fact,  its  bracts  are  found  so  often 
as  to  be  considered  by  some  authors  as  of  quite 
normal  occurrence.  Contrasted  with  those  of 
the  above  mentioned  species  of  Sisymbrium, 
they  are  not  seen  at  the  base  of  all  the  flower- 


638  Mutations 

stalks,  but  are  limited  to  the  lowermost  part  of 
the  raceme,  adorning  a  few,  often  ten  or  twelve, 
and  rarely  more  flower-stalks.  Moreover  they 
exhibit  a  feature  which  is  indicative  of  the  pres- 
ence of  an  abnormality.  They  are  not  all  of  the 
same  size,  but  decrease  in  length  from  the  base 
of  the  raceme  upward,  and  finally  slowly  dis- 
appear. 

Besides  these  rare  cases  there  are  quite  a 
number  of  cruciferous  species  on  record,  which 
have  been  observed  to  bear  bracts.  Penzig 
in  his  valuable  work  on  teratology  gives  a 
list  of  33  such  genera,  many  of  them  repeat- 
ing the  anomaly  in  more  than  one  species. 
Ordinary  cabbages  are  perhaps  the  best  known 
instance,  and  any  unusual  abundance  of  nour- 
ishment, or  anomalous  cause  of  growth  seems 
to  be  liable  to  incite  the  development  of  bracts. 
The  hedge  garlic  or  garlic  mustard  (Alliaria), 
the  shepherd's  purse,  the  wormseed  or  Erysi- 
mum cheiranthoides  and  many  others  afford 
instances.  In  my  cultures  of  Heeger's  shep- 
herd's purse,  the  new  species  derived  at  Lan- 
dau in  Germany  from  the  common  shepherd's 
purse,  the  anomaly  was  observed  to  occur  more 
than  once,  showing  that  the  mutation,  which 
changed  the  fruits,  had  not  in  the  least  affected 
this  subordinate  anomalous  peculiarity.  In  all 
these  cases  the  bracts  behave  as  with  the  Eru- 


Systematic  Atavisjn  639 

castrum,  being  limited  to  the  base  of  the  spike, 
and  decreasing  in  size  from  the  lower  flowers 
upward.  Connected  with  these  atavistic  bracts 
is  a  feature  of  minor  importance,  which  how- 
ever, by  its  almost  universal  accompaniment  of 
the  bracts,  deserves  our  attention,  as  it  is  indica- 
tive of  another  latent  character.  As  a  rule,  the 
bracts  are  grown  together  with  their  axillary 
flower-stalk.  This  cohesion  is  not  complete,  nor 
is  it  always  developed  in  the  same  degree. 
Sometimes  it  extends  over  a  large  part  of  the 
two  organs,  leaving  only  their  tips  free,  but  on 
other  occasions  it  is  limited  to  a  small  part  of 
the  base.  But  it  is  very  interesting  that  this 
same  cohesion  is  to  be  seen  in  the  shepherd's 
purse,  in  the  wormseed  and  in  the  cabbage,  as 
well  as  in  the  case  of  the  Erucastrum  and  most 
of  the  other  observed  cases  of  atavistic  bracts. 
This  fact  suggests  the  idea  of  a  common  origin 
for  these  anomalies,  and  would  lead  to  the 
hypothesis  that  the  original  ancestors  of  the 
whole  family,  before  losing  the  bracts,  exhibited 
this  peculiar  mode  of  cohesion. 

Bracts  and  analogous  organs  afford  similar 
cases  of  systematic  atavism  in  quite  a  number 
of  other  families.  Aroids  sometimes  produce 
long  bracts  from  various  places  on  their 
spadix,  as  may  be  seen  in  the  cultivated 
greenhouse  species,  Atifhurium  scherzerianum. 


640  Mutations 

Poppies  have  been  recorded  to  bear  bracts 
analogous  to  the  little  scales  on  the  flower-stalks 
of  the  pansies,  on  the  middle  of  their  flower- 
stalks.  A  similar  case  is  shown  by  the  yellow 
foxglove  or  Digitalis  parviflora.  The  foxgloves 
as  a  rule  have  naked  flower-stalks,  without  the 
two  little  opposite  leafy  organs  seen  in  so  many 
other  instances.  The  yellow  species,  however, 
has  been  seen  to  produce  such  scales  from  time 
to  time.  The  honeysuckle  genus  is,  as  a  rule, 
devoid  of  the  stipules  at  the  base  of  the  petiole, 
but  Lonicera  etrusca  has  been  observed  to 
develop  such  organs,  which  were  seen  to  be  free 
in  some,  but  in  other  specimens  were  adnate 
to  the  base  of  the  leaf,  and  even  connate  with 
those  of  the  opposite  leaf. 

Other  instances  could  be  given  proving  that 
bracts  and  stipules,  when  systematically  lack- 
ing, are  liable  to  reappear  as  anomalies.  In 
doing  so,  they  generally  assume  the  peculiar 
characters  that  would  be  expected  of  them  by 
comparison  with  allied  genera  in  which  they  are 
of  normal  occurrence.  There  can  be  no  doubt 
that  their  absence  is  due  to  an  apparent  loss, 
resulting  from  the  reduction  of  a  formerly 
active  quality  to  inactivity.  Resuming  this  ef- 
fective state,  the  case  attains  the  value  and  sig- 
nificance accorded  to  systematic  atavism. 

A  very  curious  instance  of  reduced  bracts,  de- 


Systematic  Atavism  641 

veloping  to  unusual  size,  is  afforded  by  a  variety 
of  corn,  which  is  called  Zea  Mays  cryptosperma, 
or  Zea  Mays  tunicata.  In  ordinary  cora  the 
kernels  are  surrounded  by  small  and  thin,  incon- 
spicuous and  membranaceous  scales.  Invisible 
on  the  integrate  spikes,  when  ripe,  they  are 
easily  detected  by  pulling  the  kernels  out.  In 
cryptosperma  they  are  so  strongly  developed  as 
to  completely  hide  the  kernels.  Obviously  they 
constitute  a  case  of  reversion  to  the  characters 
of  some  unknown  ancestor,  since  the  corn  is  the 
only  member  of  the  grass-family  with  naked 
kernels.  The  var.  tunicata,  for  this  same  rea- 
son, has  been  considered  to  be  the  original  wild 
form,  from  which  the  other  varieties  of  corn 
have  originated.  But  as  no  historical  evidence 
on  this  point  is  at  hand,  we  must  leave  it  as  it  is, 
notwithstanding  the  high  degree  of  attractive- 
ness attached  to  the  suggestion. 

The  horsetail-family  may  be  taken  as  a  fur- 
ther support  of  our  assertion.  Some  species 
have  stems  of  two  kinds,  the  fertile  being 
brownish  and  appearing  in  early  spring  before 
the  green  or  sterile  ones.  In  others  the  stems 
are  all  alike,  green  and  crowned  with  a  cone- 
like spike  of  sporangia-bearing  scales.  Mani- 
festly the  dimorphous  cases  are  to  be  considered 
as  the  j^ounger  ones,  partly  because  they  are 
obvious   exceptions   to   the   common   rule,   and 


642  Mutations 

partly  because  the  division  of  labor  is  indicative 
of  a  higher  degree  of  evolution.  But  sometunes 
these  dimorphic  species  are  seen  to  revert  to  the 
primary  condition,  developing  a  fertile  cone  at 
the  summit  of  the  green  summer-stem.  I  have 
had  the  opportunity  of  collecting  an  instance  of 
this  anomaly  on  the  tall  Equisetum  telmateja 
in  Switzerland,  and  other  cases  are  on  record  in 
teratological  literature.  It  is  an  obvious  ex- 
ample of  systematic  atavism,  occurring  sud- 
denly and  with  the  full  development  of  all  the 
qualities  needed  for  the  normal  production  of 
sporangia  and  spores.  All  of  these  must  be 
concealed  in  a  latent  condition  within  the  young 
tissues  of  the  green  stems. 

More  than  once  I  have  had  occasion  to  deal 
with  the  phenomenon  of  torsions,  as  exhibited 
by  the  teasels  and  some  other  plants.  This 
anomaly  has  been  shown  to  be  analogous  to  the 
cases  described  as  double  adaptations.  The 
capacity  of  evolving  antagonistic  characters  is 
prominent  in  both.  The  antagonists  are  as- 
sumed to  lie  quietly  together  while  inactive. 
But  as  soon  as  evolution  calls  them  into  activity 
they  become  mutually  exclusive,  because  only 
one  of  them  can  come  to  full  display  in  the  same 
organ.  External  influences  decide  which  of  the 
two  becomes  dominant  and  which  remains  dor- 
mant.   This  decision  must  take  place  separately 


Systematic  Atavism  643 

for  each  stem  and  each  branch,  but  as  a  rule, 
the  stronger  axes  are  more  liable  to  furnish 
anomalies  than  the  weaker. 

Exactly  the  same  thing  is  true  of  double 
adaptations.  Every  bud  of  the  water-persi- 
caria  may  develop  either  into  an  erect  or  into  a 
floating  stem,  according  as  it  is  surrounded  by 
water  or  by  relatively  dry  soil.  In  other  cases 
utility  is  often  less  manifest,  but  some  use  may 
either  be  proved,  or  shown  to  be  very  probable. 
At  all  events  the  term  adaptation  includes  the 
idea  of  utility,  and  obviously  useless  contriv- 
ances could  hardly  be  brought  under  the  same 
head. 

We  have  also  dealt  with  the  question  of 
heredity.  It  is  obvious  that  from  the  flowers  of 
the  floating  and  erect  stems  of  the  water-persi- 
caria  seeds  will  result,  each  capable  of  yielding 
both  forms.  Quite  the  same  thing  was  the  case 
with  the  teasels.  Some  4(¥  of  the  progeny  pro- 
duce beautifully  twisted  stems,  but  whether  the 
seed  was  saved  from  the  most  completely 
twisted  specimens  or  from  the  straight  plants 
of  the  race  was  of  no  importance. 

This  phenomenon  of  twisting  may  now  be 
considered  from  quite  another  point  of  y'lew- 
It  is  a  case  of  svstematic  atavism,  or  of  the  re- 
acquirement  of  some  ancient  and  long-lost  qual- 
ity.    This  quality  is  the  alternate  position  of 


644  Mutations 

the  leaves,  which  has  been  replaced  in  the  teasel- 
family  by  a  grouping  in  pairs.  In  order  to 
prove  the  validity  of  this  assertion,  it  will  be 
necessary  to  discuss  two  points  separately,  viz. : 
relative  positions  of  the  leaves,  and  the  manner 
in  which  the  alternate  position  causes  the  stems 
to  become  twisted. 

Leaves  are  affixed  to  their  stems  and  branches 
in  various  ways.  Among  them  one  is  of 
wide  occurrence  throughout  the  whole  realm 
of  the  higher  plants,  while  all  the  others  are 
more  rare.  '  Moreover  these  subordinate  ar- 
rangements are,  as  a  rule,  confined  to  definite 
systematic  groups.  Such  groups  may  be  large, 
as  for  instance,  the  monocotyledons,  that  have 
their  leaves  arranged  in  two  opposite  rows  in 
many  families,  or  small,  as  genera  or  subdivi- 
sions of  genera.  Apart  from  these  special 
cases  the  main  stem  and  the  greater  part  of  the 
branches  of  the  pedigree  of  the  higher  plants 
exhibit  a  spiral  condition  or  a  screw  arrange- 
ment, all  leaves  being  inserted  at  different 
points  and  on  different  sides  of  the  stem.  This 
condition  is  assumed  to  be  the  original  one, 
from  which  the  more  specialized  types  have 
been  derived.  As  is  usual  with  characters  in 
general,  it  is  seen  to  vary  around  an  average, 
the  spiral  becoming  narrower  and  looser.  A 
narrow  spiral   condenses  the  leaves,  while  a 


Systematic  Atavism  645 

loose  one  disperses  them.  According  to  such 
fluctuating  deviations  the  number  of  leaves,  in- 
serted upon  a  given  number  of  spiral  circuits,  is 
different  in  different  species.  In  a  vast  major- 
ity of  cases  13  leaves  are  found  on  5  circuits, 
and  as  we  have  only  to  deal  with  this  propor- 
tion in  the  teasels  we  will  not  consider  others. 

In  the  teasels  this  screw-arrangement  has  dis- 
appeared, and  has  been  replaced  by  a  decussate 
grouping.  The  leaves  are  combined  into  pairs, 
each  pair  occupying  the  opposite  sides  of  one 
node.  The  succeeding  pairs  alternate  with  one 
another,  so  as  to  place  their  leaves  at  right 
angles.  The  leaves  are  thus  arranged  on  the 
whole  stem  in  four  equidistant  rows. 

On  the  normal  stem  of  a  teasel  the  two  mem- 
bers of  a  pair  are  tied  to  one  another  in  a  com- 
paratively complicated  way.  The  leaves  are 
broadly  sessile  and  their  bases  are  united  so  as 
to  constitute  a  sort  of  cup.  The  margins  of 
these  cups  are  bent  upward,  thereby  enabling 
them  to  hold  water,  and  after  a  rainfall  they 
may  be  seen  filled  to  the  brim.  It  is  believed 
that  these  little  reservoirs  are  useful  to  the 
plant  during  the  flowering  period,  because  they 
keep  the  ants  away  from  the  honey.  Consider- 
ing the  internal  structure  of  the  stem  at  the  base 
of  these  cups  we  find  that  the  vascular  bundles 
of  the  two  opposite  leaves  are  strongly  con- 


64:6  Mutations 

nected  with  one  another,  constituting  a  ring 
which  narrowly  surrounds  the  stem,  and  which 
would  impede  an  increase  in  thickness,  if  such 
were  in  the  nature  of  the  plant.  But  since  the 
stems  end  their  existence  during  the  summer  of 
their  development,  this  structure  is  of  no  real 
harm. 

The  grouping  of  the  leaves  in  alternate  pairs 
may  be  seen  within  the  bud  as  well  as  on  the 
adult  stems.  In  order  to  do  this,  it  is  necessary 
to  make  transverse  sections  through  the  heart 
of  the  rosette  of  the  leaves  of  the  first  year. 
If  cut  through  the  base,  the  pair  exhibit  connate 
wings,  corresponding  to  the  water-cups;  if  cut 
above  these,  the  leaves  seem  to  be  free  from  one 
another. 

In  order  to  compare  the  position  of  leaves 
of  the  twisted  plants  with  this  normal  arrange- 
ment, the  best  way  is  to  make  a  corresponding 
section  through  the  heart  of  the  rosette  of  the 
first  year.  It  is  not  necessary  to  make  a  micro- 
scopic preparation.  In  the  fall  the  changed  dis- 
position may  at  once  be  seen  to  affect  the  central 
leaves  of  the  group.  All  the  rosettes  of  the 
whole  race  commence  with  opposite  leaves; 
those  that  are  to  produce  straight  stems  remain 
in  this  condition,  but  the  preparation  for  twist- 
ing begins  at  the  end  of  the  first  year  as  shown 
by  a  special  arrangement  of  the  leaves.     This 


Systematic  Atavism  647 

disposition  may  then  be  seen  to  extend  to  the 
very  center  of  the  rosette,  by  use  of  microscop- 
ical sections.  Examining  sections  made  in  the 
spring,  the  original  arrangement  of  the  leaves 
of  the  stem  is  observed  to  continue  until 
the  beginning  of  the  growth  of  the  shoot. 
It  is  easy  to  estimate  the  number  of  leaves  cor- 
responding to  a  given  number  of  spiral  circuits 
in  these  sections  and  the  proportion  is  found  to 
indicate  13  leaves  on  5  turns.  These  figures 
are  the  same  as  those  given  above  for  the  ordi- 
nary arrangement  of  alternate  leaves  in  the 
main  lines  of  the  pedigree  of  the  vegetable  king- 
dom. 

Leaving  aside  for  the  moment  the  subsequent 
changes  of  this  spiral  arrangement,  it  becomes 
at  once  clear  that  here  we  have  a  case  of  sys- 
tematic atavism.  The  twisted  teasels  lose  their 
decussation,  but  in  doing  so  the  leaves  are  not 
left  in  a  disorderly  dispersion,  but  a  distinct  new 
arrangement  takes  its  place,  which  is  to  be 
assumed  as  the  normal  one  for  the  ancestors 
of  the  teasel  family.  The  case  is  to  be  consid- 
ered as  one  of  atavism.  Obviously  no 
other  explanation  is  possible,  than  the  sup- 
position that  the  5-13  spiral  is  still  latent, 
though  not  displayed  by  the  teasels.  But  in 
the  very  moment  when  the  faculty  of  decussa- 
tion disappears,  it  resumes  its  place,  and  be- 


648  Mutations 

comes  as  prominent  as  it  must  once  have  been  in 
the  ancestors,  and  is  still  in  that  part  of  their 
offspring,  which  has  not  become  changed  in  this 
respect.  Thus  the  proof  of  our  assertion  of 
systematic  atavism  is,  in  this  case,  not  obtained 
by  the  inspection  of  the  adult,  but  by  the  investi- 
gation of  the  conditions  in  an  early  stage. 
It  remains  to  be  explained  how  the  twisting  may 
finally  be  caused  by  this  incipient  grouping  of 
the  leaves.  Before  doing  so,  it  may  be  as  well 
to  state  that  the  case  of  the  teasel  is  not  an  iso- 
lated one,  and  that  the  same  conclusions  are 
supported  by  the  valerian,  and  a  large  num- 
ber of  other  examples.  In  early  spring  some 
rosettes  show  a  special  condition  of  the 
leaves,  indicating  thereby  at  once  their  atavism 
and  their  tendency  to  become  twisted  as  soon 
as  they  begin  to  expand.  The  Sweet  William 
or  DiantJius  barbatus  affords  another  instance; 
it  is  very  interesting  because  a  twisted  race 
is  available,  which  may  produce  thousands  of 
instances  developed  in  all  imaginable  degrees, 
in  a  single  lot  of  plants.  Viscaria  oculata 
is  another  instance  belonging  to  the  same  fam- 

iiy. 

The  bedstraw  (Galium)  also  includes  many 
species  which  from  time  to  time  produce  twist- 
ed stems.  I  have  found  them  myself  in  Holland 
on  Galium  verum  and  G.  Aparine.     Both  seem 


Systematic  Atavism  649 

to  be  of  rare  occurrence,  as  I  have  not  suc- 
ceeded in  getting  any  repetition  by  prolonged 
culture. 

Species,  which  generally  bear  their  leaves  in 
whorls,  are  also  subjected  to  casual  atavisms  of 
this  kind,  as  for  instance  the  tall  European 
horsetail,  Equisetum  Telmateja,  which  occasion- 
ally bears  cones  on  its  green  summer  stems. 
Its  whorls  are  changed  on  the  twisted  parts  into 
clearly  visible  spirals.  The  ironwood  or  Cas- 
uarina  quadrivalvis  is  sometimes  observed  to 
produce  the  same  anomaly  on  its  smaller  lateral 
branches. 

Coming  now  to  the  discussion  of  the  way  in 
which  the  twisting  is  the  result  of  the  spiral  dis- 
position of  the  leaves,  we  may  consider  this  ar- 
rangement on  stems  in  the  adult  state.  These 
at  once  show  the  spiral  line  and  it  is  easy  to  fol- 
low this  line  from  the  base  up  to  the  apex.  In 
the  most  marked  cases  it  continues  without  in- 
terruption, not  rarely  however,  ending  in  a 
whorl  of  three  leaves  and  a  subsequent  straight 
internode,  of  which  there  may  even  be  two  or 
three.  The  spiral  exhibits  the  basal  parts  of  the 
leaves,  with  the  axillary  lateral  branches.  The 
direction  of  the  screw  is  opposed  to  that  of  the 
twisting,  and  the  spiral  ribs  are  seen  to  cross  the 
line  of  insertion  of  the  leaves  at  nearly  right 
angles.     On   this    line    the  leaves    are   nearer 


650  Mutations 

to  one  another  than  would  correspond  to  the 
original  proportion  of  5  turns  for  13  leaves. 
In  fact,  10  or  even  13  leaves  may  not  rarely 
be  counted  on  a  single  turn.  Or  the  twist 
may  become  so  strong  locally  as  to  change  the 
spiral  into  a  longitudinal  line.  On  this  line 
all  inserted  leaves  extend  themselves  in  the 
same  direction,  resembling  an  extended  flag. 

The  spiral  on  the  stem  is  simply  the  continua- 
tion of  the  spiral  line  from  within  the  rosettes 
of  the  first  year.  Accordingly  it  is  seen  to  be- 
come gradually  less  steep  at  the  base.  For  this 
reason  it  must  be  one  and  the  same  with  this 
line,  and  in  extreme  youth  it  must  have  pro- 
duced its  leaves  at  the  same  mutual  distances  as 
this  line.  Transverse  sections  of  the  growing 
summits  of  the  stems  support  this  conclusion. 

From  these  several  facts  we  may  infer  that 
the  steepness  of  the  spiral  line  increases  on  the 
stem,  as  it  is  gradually  changed  into  a  screw. 
Originally  5  turns  were  needed  for  13  leaves, 
but  this  number  diminishes  and  4  or  3  or  even  2 
turns  may  take  the  same  number  of  foliar 
organs,  until  the  screw  itself  is  changed  into  a 
straight  line. 

This  change  consists  in  an  unwinding  of  the 
whole  spiral,  and  in  order  to  effect  this  the  stem 
must  become  wound  up  in  the  opposite  direc- 
tion.    The  winding  of  the  foliar   screw  must 


Systematic  Atavism  651 

curve  the  longitudinal  ribs.  The  straighter 
and  steeper  the  screw  becomes,  the  more  the 
ribs  will  become  twisted.  That  this  happens  in 
the  opposite  direction  is  obvious,  without  fur- 
ther discussion.  The  twisting  is  the  inevitable 
consequence  of  the  reversal  of  the  screw. 

Two  points  remain  to  be  dealt  with.  One  is 
the  direct  proof  of  the  reversal  of  the  screw,  the 
other  the  discussion  of  its  cause.  The  first  may 
be  observed  by  a  simple  experiment.  Of  course 
it  proceeds  only  slowly,  but  all  that  is  necessary 
is  to  mark  the  position  of  one  of  the  younger 
leaves  of  a  growing  stem  of  a  twisting  indi- 
vidual and  to  observe  the  change  in  its  posi- 
tion in  a  few  hours.  It  will  be  seen  to  have 
turned  some  way  around  the  stem,  and  finally 
may  be  seen  to  make  a  complete  revolution  in 
the  direction  opposite  to  the  screw,  and  there- 
by  demonstrating   the   fact   of   its   uncurling. 

The  cause  of  this  phenomenon  is  to  be  sought 
in  the  intimate  connection  of  the  basal  parts  of 
the  leaves,  which  we  have  detailed  above.  The 
fibrovascular  strands  constitute  a  strong  rope, 
which  is  twisted  around  the  stem  along  the 
line  on  which  the  leaves  are  inserted.  The 
strengthening  of  the  internodes  may  stretch  this 
rope  to  some  extent,  but  it  is  too  strong  to  be 
rent  asunder.  Hence  it  opposes  the  normal 
growth,  and  the  only  manner  in  which  the  inter- 


652  Mutations 

nodes  may  adjust  themselves  to  the  forces  which 
tend  to  cause  their  expansion  is  by  straighten- 
ing the  rope.  In  doing  so  they  may  find  the  re- 
quired space,  by  growing  out  in  an  unusual 
direction,  bending  their  axes  and  twisting  the 
ribs. 

To  prove  the  validity  of  this  explanation,  a 
simple  experiment  may  be  given.  If  the  fibro- 
vascular  rope  is  the  mechanical  impedimeni 
which  hinders  the  normal  growth,  we  may  tr^ 
the  effect  of  cutting  through  this  rope.  By  this 
means  the  hindrance  may  at  least  locally 
be  removed.  Now,  of  course,  the  operatior 
must  be  made  in  an  early  stage  before 
or  at  the  beginning  of  the  period  of  growth 
in  every  case  before  the  uncurling  of  th( 
rope  begins.  Wounds  made  at  this  time  are  ap1 
to  give  rise  to  malformations,  but  notwithstand 
ing  this  difficulty  I  have  succeeded  in  giving  th( 
necessary  proof.  Stems  operated  upon  become 
straight  where  the  rope  is  cut  through,  thougl 
above  and  under  the  wounded  part  they  go  oi 
twisting  in  the  usual  way. 

Sometimes  the  plants  themselves  succeed  ii 
tearing  the  rope  asunder,  and  long  straight  in 
ternodes  divide  the  twisted  stems  in  two  or  mor( 
parts  in  a  very  striking  manner.  A  line  of  ton 
leaf-bases  connects  the  two  parts  of  the  serev 
and  gives  testimony  of  what  has  passed  withii 


Systematic  Atavism  653 

the  tissues.  At  other  times  the  straightening 
may  have  taken  place  directly  internal  to  a  leaf, 
and  it  is  torn  and  may  be  seen  to  be  attached  to 
the  stem  by  two  distinct  bases. 

Summing  up  this  description  of  the  heredi- 
tary qualities  of  our  twisted  teasels  arid  of  their 
mechanical  consequences,  we  may  say  that  the 
loss  of  the  normal  decussation  is  the  cause  of  all 
the  observed  changes.  This  special  adaptation, 
which  places  the  leaves  in  alternating  pairs,  re- 
placed and  concealed  the  old  and  universal  ar- 
rangement on  a  screw  line.  In  disappearing,  it 
leaves  the  latter  free,  and  according  to  the  rule 
of  systematic  atavism,  this  now  becomes  active 
and  takes  its  place.  If  the  fibrovascular  con- 
nection of  the  leaf-bases  were  lost  at  the  same 
time  the  stems  would  grow  and  become  straight 
and  tall.  This  change  however,  does  not  occur, 
and  the  bases  of  the  leaves  now  constitute  a  con- 
tinuous rope  instead  of  separate  rings,  and 
thereby  impede  the  stretching  of  the  intemodes. 
These  in  their  turn  avoid  the  difficulty  by  twist- 
ing themselves  in  a  direction  opposite  to  that 
of  the  spiral  of  the  leaves. 

As  a  last  example  of  systematic  atavism  I  will 
refer  to  the  reversionary  changes,  afforded  by 
the  tomatoes.  Though  the  culture  of  this  plant 
is  a  recent  one,  it  seems  to  be  at  present  in  a 
state  of  mutability,  producing  new  strains,  or 


654  Mutations 

assuming  the  features  of  their  presumable  an- 
cestors. In  his  work  ^  ^  The  Survival  of  the  Un- 
like," Bailey  has  given  a  detailed  description  of 
these  various  types.  Moreover,  he  has  closely 
studied  the  causes  of  the  changes,  and  shown 
the  great  tendency  of  the  tomatoes  to  vicinism. 
By  far  the  larger  part  of  the  observed  cases  of 
running  out  of  varieties  are  caused  by  acciden- 
tal crosses  through  the  agency  of  insects.  Even 
improvements  are  not  rarely  due  to  this  cause. 
Besides  these  common  and  often  unavoidable 
changes,  others  of  greater  importance  occur 
from  time  to  time.  Two  of  them  deserve  to  be 
mentioned.  They  are  called  the  '*  Upright  "  and 
the  '^  Mikado  '^  types,  and  differ  as  much  or 
even  more  from  their  parents  than  the  latter  do 
from  any  one  of  their  wild  congeners.  Their 
characters  come  true  from  seed.  The  *^  Mika- 
do ' '  race  or  the  Lycopersicum  grandifolium  (L. 
latifolium)  has  larger  and  fewer  leaflets  than 
the  slender  and  somewhat  flimsy  foliage  of  the 
common  form.  Flat  or  plane  blades  with  de- 
current  margins  constitute  another  character. 
This  variety,  however,  does  not  concern  our 
present  discussion.  The  upright  type  has  stiff 
and  self-sustaining  stems  and  branches,  resem- 
bling rather  a  potato-plant  than  a  tomato. 
Hence  the  name  Lycopersicum  solanopsis  or  L, 
validum,  under  which  it  is  usually  described. 


Systematic  Atavism  655 

The  foliage  of  the  plant  is  so  distinct  as  to  yield 
botanical  characters  of  sufficient  importance  to 
justify  this  specific  designation.  The  leaflets 
are  reduced  in  numbers  and  greatly  modi- 
fied, and  the  flowers  in  the  inflorescence  are  re- 
duced to  two  or  three.  This  curious  race  came 
in  suddenly,  without  any  premonition,  and  the 
locality  and  date  of  its  mutation  are  still  on 
record.  Until  some  years  ago  it  had  not  made 
its  appearance  for  a  second  time.  Obviously  it 
is  to  be  considered  as  a  reversionary  form. 
The  limp  stems  of  the  common  tomatoes  are  in 
all  respects  indicative  of  the  cultivated  condi- 
tion. They  cannot  hold  themselves  erect,  but 
must  be  tied  up  to  supports.  The  color  of 
the  leaves  is  a  paler  green  than  should  be  ex- 
pected from  a  wild  plant.  Considering  other 
species  of  the  genus  Solaniim,  of  which  the 
Lycopersicum  is  a  subdivision,  the  stems  are  as 
a  rule  erect  and  self-supporting,  with  some  few 
exceptions.  These,  however,  are  special  adapta- 
tions as  shown  by  the  winding  stems  of  the 
bitter-sweet. 

From  this  discussion  we  seem  justified  in  con- 
cluding that  the  original  appearance  of  the  up- 
right type  was  of  the  nature  of  systematic 
atavism.  It  differs  however,  from  the  already 
detailed  cases  in  that  it  is  not  a  monstrosity,  nor 
an  ever-sporting  race,  but  is  as  constant  a  form 


656  Mutations 

as  the  best  variety  or  species.  Even  on  this 
ground  it  must  be  considered  as  a  representa- 
tive of  a  separate  group  of  instances  of  the  uni- 
versal rule  of  systematic  reversions. 

Of  late  the  same  mutation  has  occurred  in  the 
garden  of  C.  A.  White  at  Washington.  The 
parent  form  in  this  case  was  the  ^*  Acme,"  of 
the  ordinary  weak  and  spreading  habit  of 
growth.  It  is  known  as  one  of  the  best  and  most 
stable  of  the  varieties  and  was  grown  by  Mr. 
White  for  many  years,  and  had  not  given  any 
sign  of  a  tendency  towards  change.  Seeds 
from  some  of  the  best  plants  in  1899  were  sown 
the  following  spring,  and  the  young  seedlings 
unexpectedly  exhibited  a  marked  difference 
from  their  parents.  From  the  very  outset  they 
were  more  strong  and  erect,  more  compact  and 
of  a  darker  green  than  the  ^^  Acme."  When 
they  reached  the  fruiting  stage  they  had  devel- 
oped into  typical  representatives  of  the  Lyco- 
persicum  solanopsis  or  upright  division.  The 
whole  lot  of  plants  comprised  only  some  30 
specimens,  and  this  number,  of  course,  is  too 
small  to  base  far-reaching  conclusions  upon. 
But  all  of  the  lot  showed  this  type,  no 
true  **  Acme  "  being  seen  among  them.  The 
fruit  differed  in  flavor,  consistencv  and  color 
from  that  of  the  parent,  and  it  also  ripened 
earlier  than  the  latter.    No  seed  was  saved  from 


Systematic  Atavism  657 

these  plants,  but  the  following  year  the 
'*  Acme  "  was  sown  again  and  found  true  to  its 
type.  Seeds  saved  from  this  generation  in  1900 
have,  however,  repeated  the  mutation,  giving 
rise  to  exactly  the  same  new  upright  form  in 
1901.  This  was  called  by  its  originator  ^^  The 
Washington."  Seeds  from  this  second  muta- 
tion were  kindly  sent  to  me  by  Mr.  White,  and 
proved  true  to  their  type  when  sown  in  my 
garden.  , 

Obviously  it  is  to  be  assumed  in  the  case  of 
the  tomatoes  as  well  as  in  instances  from 
other  genera  cited,  that  characters  of  an- 
cestors, which  are  not  displayed  in  their 
progeny,  have  not  been  entirely  lost,  but  are  still 
present,  though  in  a  latent  condition.  They 
may  resume  their  activity  unexpectedly,  and  at 
once  develop  all  the  features  which  they  for- 
merly had  borne. 

Latency,  from  this  point  of  view,  must  be  one 
of  the  most  common  things  in  nature.  All  or- 
ganisms are  to  be  considered  as  internally 
formed  of  a  host  of  units,  partly  active  and 
partly  inactive.  Extremely  minute  and  almost 
inconceivably  numerous,  these  units  must  have 
their  material  representatives  within  the  most 
intimate  parts  of  the  cells. 


Lecture  XXIII 


TAXONOMIC   ANOMALIES 


The  theory  of  descent  is  founded  mainly 
on  comparative  studies,  which  have  the  ad- 
vantage of  affording  a  broad  base  and  the 
convincing  effect  of  concurrent  evidence 
brought  together  from  widely  different  sources. 
The  theory  of  mutation  on  the  other  hand  rests 
directly  upon  experimental  investigations,  and 
facts  concerning  the  actual  descent  of  one  form 
from  another  are  as  yet  exceedingly  rare.  It  is 
always  difficult  to  estimate  the  validity  of  con- 
clusions drawn  from  isolated  instances  selected 
from  the  whole  range  of  contingent  phenomena, 
and  this  is  especially  true  of  the  present  case. 
Systematic  and  physiologic  facts  seem  to  indi- 
cate the  existence  of  universal  laws,  and  it  is  not 
probable  that  the  process  of  production  of  new 
species  would  be  different  in  the  various  parts 
of  the  animal  and  vegetable  kingdoms.  More- 
over the  principle  of  unit-characters,  the  pre- 
eminent significance  of  which  has  come  to  be 
more  fully  recognized  of  late,  is  in  full  harmony 

658 


Taxonomic  Anomalies  659 

with  the  theory  of  sudden  mutations.  Together 
these  two  conceptions  go  to  strengthen  the  prob- 
ability of  the  sudden  origin  of  all  specific  char- 
acters. 

Experimental  researches  are  limited  in  their 
extent,  and  the  number  of  cases  of  direct  obser- 
vation of  the  process  of  mutation  will  probably 
never  become  large  enough  to  cover  the  whole 
field  of  the  theory  of  descent.  Therefore  it  will 
always  be  necessary  to  show  that  the  similarity 
between  observed  and  other  cases  is  such  as  to 
lift  above  all  doubt  the  assertion  of  their  result- 
ing from  the  same  causes. 

Besides  the  direct  comparison  of  the  muta- 
tions described  in  our  former  lectures,  with  the 
analogous  cases  of  the  horticultural  and  natural 
production  of  species  and  varieties  at  large,  an- 
other way  is  open  to  obtain  the  required  proof. 
It  is  the  study  of  the  phenomena,  designated  by 
Casimir  de  Candolle  by  the  name  of  taxo- 
nomic anomalies.  It  is  the  assertion  that  char- 
acters, which  are  specific  in  one  case,  may  be 
observed  to  arise  as  anomalies  or  as  varieties  in 
other  instances.  If  they  can  be  shown  to  be 
identical  or  nearly  so  in  both,  it  is  obviously 
allowable  to  assume  the  same  origin  for  the 
specific  character  and  for  the  anomaly.  In 
other  terms,  the  specific  marks  may  be  consid- 
ered as  having  originated  according  to  the  laws 


660  Mutations 

that  govern  the  production  of  anomalieSj  and 
we  may  assume  them  to  lie  within  reach  of  our 
experiments.  The  experimental  treatment  of 
the  origin  of  species  may  also  be  looked  upon  as 
a  method  within  our  grasp. 

The  validity  and  the  significance  of  these 
considerations  will  at  once  become  clear,  if  we 
choose  a  definite  example.  The  broadest  and 
most  convincing  one  appears  to  me  to  be  af- 
forded by  the  cohesion  of  the  petals  in  gamo- 
petalous  flowers.  According  to  the  current 
views  the  families  with  the  petals  of  their 
flowers  united  are  regarded  as  one  or  two  main 
branches  of  the  whole  pedigree  of  the  vege- 
table kingdom.  Eichler  and  others  assume 
them  to  constitute  one  branch,  and  therefore  one 
large  subdivision  of  the  system.  Bessey,  on  the 
other  hand,  has  shown  the  probability  of  a  sep- 
arate origin  for  those  groups  which  have  in- 
ferior ovaries.  Apart  from  such  divergencies 
the  connation  of  the  petals  is  universally  recog- 
nized as  one  of  the  most  important  systematic 
characters. 

How  may  this  character  have  originated? 
The  heath-family  or  the  Ericaceae  and  their 
nearest  allies  are  usually  considered  to  be  the 
lowest  of  the  gamopetalous  plants.  In  them  the 
cohesion  of  the  petals  is  still  subject  to  rever- 
sionary exceptions.     Such  cases  of  atavism  may 


Taxonomic  Anomalies  661 

be  observed  either  as  specific  marks,  or  in  the 
way  of  anomalies.  Ledum,  Monotropa  and  Py- 
rola,  or  the  Labrador  tea,  the  Indian  pipe  and 
wintergreen  are  instances  of  reversionary 
gamopetalism  with  free  petals.  In  heaths 
{Erica  Tetralix)  and  in  rhododendrons  the 
same  deviation  is  observed  to  occur  from  time 
to  time  as  an  anomaly,  and  even  the  common 
Rhododendron  ponticum  of  our  gardens  has  a 
variety  in  which  the  corolla  is  more  or  less 
split.  Sometimes  it  exhibits  five  free  petals, 
while  at  other  times  only  one  or  two  are  entirely 
free,  the  remaining  four  being  incompletely 
loosened. 

Such  cases  of  atavism  make  it  probable  that 
the  coherence  of  the  petals  has  originally  arisen 
by  the  same  method,  but  by  action  in  the  op- 
posite direction.  The  direct  proof  of  this  con- 
clusion is  afforded  by  a  curious  observation, 
made  by  Vilmorin  upon  the  bright  and  large- 
flowered  garden-poppy,  Papaver  hracteatum. 
Like  all  poppies  it  has  four  petals,  which  are 
free  from  one  another.  In  the  fields  of  Messrs. 
Vilmorin,  where  it  is  largely  cultivated  for  its 
seeds,  individuals  occur  from  time  to  time  which 
are  anomalous  in  this  respect.  They  exhibit  a 
tendency  to  produce  connate  petals.  Their 
flowers  become  monopetalous,  and  the  whole 
strain  is  designated  by  the  name  of  Papaver 


662  Mutations 

hracteatum  monopetalum.  Henry  de  Vilmorin 
had  the  kindness  to  send  me  some  of  these 
plants,  and  they  have  flowered  in  my  garden 
during  several  years.  The  anomaly  is  highly 
variable.  Some  flowers  are  quite  normal,  ex- 
hibiting no  sign  of  connation ;  others  are  wholly 
gamopetalous,  the  four  petals  being  united  from 
their  base  to  the  YO^ry  margin  of  the  cup  formed. 
In  consequence  of  the  broadness  of  the  petals 
however,  this  cup  is  so  wide  as  to  be  very 
shallow. 

Intermediate  states  occur,  and  not  infre- 
quently. Sometimes  only  two  or  three  petals 
are  united,  or  the  connation  does  not  extend  the 
entire  length  of  the  petals.  These  cases  are 
quite  analogous  to  the  imperfect  splitting  of 
the  corolla  of  the  rhododendron.  Giving  free 
rein  to  our  imagination,  we  may  for  a  moment 
assume  the  possibility  of  a  new  subdivision  of 
the  vegetable  kingdom,  arising  from  Vilmorin 's 
poppy  and  having  gamopetalous  flowers  for  its 
chief  character.  If  the  character  became  fixed, 
so  as  to  lose  its  present  state  of  variability, 
such  a  group  of  supposititious  gamopetalous 
plants  might  be  quite  analogous  to  the  corre- 
sponding real  gamopetalous  families.  Hence 
there  can  be  no  objection  to  the  view,  that  the 
heaths  have  arisen  in  an  analogous  manner  from 
their  polypetalous  ancestors.     Other  species  of 


Taxonomic  Anomalies  663 

the  same  genus  have  also  been  recorded  to  pro- 
duce gamopetalous  flowers,  as  for  instance, 
Papaver  hybridum,  by  Hoffmann.  Poppies  are 
not  the  sole  example  of  accidental  gamopetaly. 
Linnaeus  observed  the  same  deviation  long  ago 
for  Saponaria  officinalis,  and  since,  it  has  been 
seen  in  Clematis  Vitalha  by  Jaeger,  in  Peltaria 
alliacea  by  Schimper,  in  Silene  annulata  by  Bo- 
reau  and  in  other  instances.  No  doubt  it  is  not 
at  all  of  rare  occurrence,  and  the  origin  of  the 
present  gamopetalous  families  is  to  be  consid- 
ered as  nothing  extraordinary.  It  is,  as  a  mat- 
ter of  fact,  remarkable  that  it  has  not  taken 
place  in  more  numerous  instances,  and  the  mal- 
lows show  that  such  opportunities  have  been 
available  at  least  more  than  once. 

Other  instances  of  taxonomic  anomalies  are 
afforded  by  leaves.  Many  genera,  the  species  of 
which  mainly  bear  pinnate  or  palmate  leaves, 
have  stray  types  with  undivided  leaves. 
Among  the  brambles,  Rubus  odoratus  and 
E.  flexuosus  may  be  cited,  among  the  aralias, 
Aralia  crassifolia  and  A.  papyrifera,  and 
among  the  jasmines,  the  deliciously  scented 
sambac  {Jasminum  Sambac),  But  the  most 
curious  instance  is  that  of  the  telegraph-plant, 
or  Desmodium  gyrans,  each  complete  leaf  of 
which  consists  of  a  large  terminal  leaflet  and 
two  little  lateral  ones.     These  latter  keep  up, 


^Q4.  Mutations 

night  and  day,  an  irregular  jerking  movement, 
which  has  been  compared  to  the  movements  of 
a  semaphore.  Desmodium  is  a  papiliona- 
ceous plant  and  closely  allied  to  the  genus 
Hedysarum,  which  has  pinnate  leaves  with 
numerous  pairs  of  leaflets.  Its  place  in  the 
system  leaves  no  doubt  concerning  its  origin 
from  pinnate-leaved  ancestors.  At  the  time  of 
its  origination  its  leaves  must  have  become  re- 
duced as  to  the  number  of  the  blades,  while  the 
size  of  the  terminal  leaflet  was  correspondingly 
increased. 

It  might  seem  difficult  to  imagine  this  great 
change  taking  place  suddenly.  However,  we  are 
compelled  to  familiarize  ourselves  with  such  hy- 
pothetical assumptions.  Strange  as  they  may 
seem  to  those  who  are  accustomed  to  the  concep- 
tion of  continuous  slow  improvements,  they  are 
nevertheless  in  complete  agreement  with  what 
really  occurs.  Fortunately  the  direct  proof  of 
this  assertion  can  be  given,  and  in  a  case 
which  is  narrowly  related,  and  quite  parallel  to 
that  of  the  Des^nodiitm,  since  it  affects  a  plant 
of  the  same  family.  It  is  the  case  of  the 
monophyllous  variety  of  the  bastard-acacia  or 
Robinia  Pseud-Acacia.  In  a  previous  lecture 
we  have  seen  that  it  originated  suddenly  in  a 
French  nursery  in  the  year  1855.  It  can  be 
propagated  by  seed,  and  exhibits  a  curious  de- 


Taxonomic  Anomalies  665 

gree  of  variability  of  its  leaves.  In  some  in- 
stances these  are  one-bladed,  the  blade  reaching 
a  length  of  15  cm.,  and  hardly  resembling  those 
of  the  common  bastard-acacia.  Other  leaves 
produce  one  or  two  small  leaflets  at  the  base  of 
the  large  terminal  one,  and  by  this  contrivance 
are  seen  to  be  very  similar  to  those  of  the  Des- 
modium,  repeating  its  chief  characters  nearly 
exactly,  and  only  differing  somewhat  in  the  rela- 
tive size  of  the  various  parts.  Lastly  real  in- 
termediates are  seen  between  the  monophyllous 
and  the  pinnate  types.  As  far  as  I  have  been 
able  to  ascertain,  these  are  produced  on  weak 
twigs  under  unfavorable  conditions;  the 
size  of  the  terminal  leaflet  decreases  and  the 
number  of  the  lateral  blades  increases,  showing 
thereby  the  presence  of  the  original  pinnate 
type  in  a  latent  condition. 

The  sudden  origin  of  this  **  one-leaved " 
acacia  in  a  nursery  may  be  taken  as  a  prototype 
of  the  ancient  origin  of  Desmodium.  Of 
course  the  comparison  only  relates  to  a  single 
character,  and  the  movements  of  the  leaflets  are 
not  affected  by  it.  But  the  monophylly,  or  rath- 
er the  size  of  the  terminal  blade  and  the  reduc- 
tion of  the  lateral  ones,  may  be  held  to  be  suf- 
ficiently illustrated  by  the  bastard-acacia.  It 
is  worth  while  to  state,  that  analogous  varieties 
have  also  arisen  in  other  genera.       The  *'  one- 


666  Mutations 

leaved  ^'  strawberry  has  already  been  referred 
to.  It  originated  from  the  ordinary  type  in 
Norway  and  at  Paris.  The  walnut  likewise,  has 
its  monophyllous  variety.  It  was  mentioned 
for  the  first  time  as  a  cultivated  tree  about  1864, 
but  its  origin  is  unknown.  A  similar  variety  of 
the  walnut,  with  '^  one-bladed  "  leaves  but  of 
varying  shapes,  was  found  wild  in  a  forest  near 
Dieppe  in  France  some  years  ago,  and  appeared 
to  be  due  to  a  sudden  mutation. 

Something  more  is  known  concerning  the 
**  one-bladed  "  ashes,  varieties  of  which  are 
often  seen  in  our  parks  and  gardens.  The  com- 
mon form  has  broad  and  deeply  serrate  leaves, 
which  are  far  more  rounded  than  the  leaflets  of 
the  ordinary  ash.  The  majority  of  the  leaves 
are  simple,  but  some  produce  one  or  two  smaller 
leaflets  at  their  base,  closely  corresponding  in 
this  respect  to  the  variations  of  the  ''  one- 
bladed  "  bastard-acacia,  and  evidently  indicat- 
ing the  same  latent  and  atavistic  character.  In 
some  instances  this  analogy  goes  still  further, 
and  incompletely  pinnate  leaves  are  produced 
with  two  or  more  pairs  of  leaflets.  Besides 
this  variable  type  another  has  been  described 
by  Willdenow.  It  has  single  leaves  exclusive- 
ly, never  producing  smaller  lateral  leaflets, 
and  it  is  said  to  be  absolutely  constant 
from    seed,    while    the    more    variable    types 


Taxonomic  Anomalies  667 

seem  to  be  also  more  inconstant  when  propa- 
gated sexually.  The  difference  is  so  striking 
and  affords  such  a  reliable  feature  that  Koch 
proposed  to  make  two  distinct  varieties  of  them, 
calling  the  pure  type  Fraxinus  excelsior  mono- 
phylla,  and  the  varying  trees  F.  excel,  exhetero- 
phylla.  Some  writers,  and  among  them  Will- 
denow,  have  preferred  to  separate  the  "  one- 
leaved  '^  forms  from  the  species,  and  to  call 
them  Fraxinus  simplicifolia. 

According  to  Smith  and  to  Loudon,  the  ^  ^  one- 
leaved  "  ashes  are  found  wild  in  different  dis- 
tricts in  England.  Intermediate  forms  have  not 
been  recorded  from  these  localities.  This 
mode  of  origin  is  that  already  detailed  for  the 
laciniate  varieties  of  alders  and  so  many  other 
trees.  Hence  it  may  be  assumed  that  the  '^  one- 
leaved  "  ashes  have  sprung  suddenly  but  fre- 
quently from  the  original  pinnate  species.  The 
pure  type  of  Willdenow  should,  in  this  case, 
be  considered  as  due  to  a  slightly  different 
mutation,  perhaps  as  a  pure  retrograde  variety, 
while  the  varying  strains  may  only  be  ever- 
sporting  forms.  This  would  likewise  explain 
part  of  their  observed  inconstancy. 

In  this  respect  the  historic  dates,  as  collected 
by  Korshinsky,  are  not  very  convincing.  Vi- 
cinism  has  of  course,  almost  never  been  exclud- 
ed, and  part  of  the  multiformity  of  the  offspring 


668  Mutations 

must  obviously  be  due  to  this  most  universal 
agency.  Indirect  vicinism  also  plays  some  part, 
and  probably  affords  the  explanation  of  some 
reputed  mutative  productions  of  the  variety. 
So,  for  instance,  in  the  case  of  Sinning,  who  aft- 
er sowing  the  seeds  of  the  common  ash,  got  as 
large  a  proportion  as  2^'  of  monophyllous  trees 
in  a  culture  of  some  thousand  plants.  It  is 
probable  that  his  seeds  were  taken  partly  from 
normal  plants,  and  partly  from  hybrids  between 
the  normal  and  the  ''  one-bladed  "  ijve,  assum- 
ing that  these  hybrids  have  pinnate  leaves  like 
their  specific  parent,  and  bear  the  characters  of 
the  other  parent  only  in  a  latent  condition. 

Our  third  example  relates  to  peltate  leaves. 
They  have  the  stalk  inserted  in  the  middle  of 
the  blade,  a  contrivance  produced  by  the  conna- 
tion  of  the  two  basal  lobes.  The  water-lilies 
are  a  well  known  instance,  exhibiting  sagit- 
tate leaves  in  the  juvenile  stage  and  changing 
in  many  species,  into  nearly  circular  pel- 
tate forms,  of  which  Victoria  regia  is  a  very 
good  example,  although  its  younger  stages  do 
not  always  excite  all  the  interest  they  deserve. 
The  Indian  cress  (Tropaeolmn),  the  marsh- 
pennywort  or  Hydrocotyle,  and  many  other  in- 
stances could  be  quoted.  Sometimes  the  peltate 
leaves  are  not  at  all  orbicular,  but  are  elon- 
gated, oblong  or  elliptic,  and  with  only  the  lobes 


Taxonomic  Anomalies  669 

at  the  base  united.  The  lemon-scented  Eucor 
lyptus  citriodora  is  one  of  the  most  widely 
known  cases.  In  other  instances  the  peltate 
leaves  become  more  or  less  hollow,  constituting 
broad  ascidia  as  in  the  case  of  the  crassulaceous 
genus  Umbilicus. 

This  connation  of  the  basal  lobes  is  universal- 
ly considered  as  a  good  and  normal  specific 
character.  Nevertheless  it  has  its  manifest 
analogy  in  the  realm  of  the  anomalies.  This  is 
the  pitcher  or  ascidiiim.  On  some  trees  it  is  of 
quite  common  occurrence,  as  on  the  lime-tree 
{Tilia  parvifolia)  and  the  magnolia  {Magnolia 
obovata  and  its  hybrids).  It  is  probable  that 
both  these  forms  have  varieties  with,  and  others 
without,  ascidia.  Of  the  lime-tree,  instances  are 
known  of  single  trees  which  produce  hundreds 
of  such  anomalous  leaves  yearly,  and  one  such  a 
tree  is  growing  in  the  neighborhood  of  Amster- 
dam at  Lage  Vuursche.  I  have  alluded  to  these 
cases  more  than  once,  but  on  this  occasion  a 
closer  inspection  of  the  structure  of  the  ascidium 
is  required.  For  this  purpose  we  may  take  the 
lime-tree  as  an  example.  Take  the  shape  of  the 
normal  leaves  in  the  first  place.  These  are  cor- 
date at  their  base  and  mainly  inequilateral,  but 
the  general  shape  varies  to  a  considerable  ex- 
tent. This  variation  is  closely  related  to  the 
position  of  the  leaves  on  the  twigs,  and  shows 


670  Mutations 

distinct  indications  of  complying  with  the  gen- 
eral law  of  periodicity.  The  first  leaves  are 
smaller,  with  more  rounded  lobes,  the  subse- 
quent leaves  attain  a  larger  size,  and  their  lobes 
slightly  change  their  forms.  In  the  first  leaves 
the  lobes  are  so  broad  as  to  touch  one  another 
along  a  large  part  of  their  margins,  but  in  or- 
gans formed  later  this  contact  gradually  dimin- 
ishes and  the  typical  leaves  have  the  lobes  wide- 
ly separated.  Now  it  is  easily  understood  that 
the  contact  or  the  separation  of  the  lobes  must 
play  a  part  in  the  construction  of  the  ascidia, 
as  soon  as  the  margins  grow  together.  Leaves 
which  touch  one  another,  may  be  affected  by 
the  connation  without  any  further  malforma- 
tion. They  remain  flat,  become  peltate  and  ex- 
hibit a  shape  which  in  some  way  holds  a  mid- 
dle position  between  the  pennyworts  and  the 
lemon-scented  eucalyptus.  Here  we  have 
the  repetition  of  the  specific  characters  of  these 
plants  by  the  anomaly  of  another.  Whenever 
the  margins  are  not  in  contact,  and  become  con- 
nate, notwithstanding  their  separation,  the  blade 
must  be  folded  together  in  some  slight  degree, 
in  order  to  produce  the  required  contact.  This 
is  the  origin  of  the  ascidium.  It  is  quite  super- 
fluous to  insist  upon  the  fact  that  their  width 
or  narrowness  must  depend  upon  the  corre- 
sponding normal  form.    The  more  distant  the 


Taxonomic  Anomalies  671 

lobes,  the  deeper  the  ascidium  will  become.  It 
should  be  added  that  this  explanation  of  the  dif- 
ferent shapes  of  ascidia  is  of  general  validity. 

Ascidia  of  the  snake-plantain  or  Plantago 
lanceolata  are  narrow  tubes,  because  the  leaves 
are  oblong  or  lanceolate,  while  those  of  the 
broad  leaved  species  of  arrowhead,  as  for  in- 
stance, the  Sagittaria  japonica,  are  of  a  conical 
shape. 

From  the  evidence  of  the  lime-tree  we  may 
conclude  that  normal  peltate  leaves  may  have 
originated  in  the  same  way.  And  from  the  fact 
that  pitchers  are  one  of  the  most  frequent 
anomalies,  we  may  conclude  that  the  chance  of 
producing  peltate  leaves  must  have  been  a  very 
great  one,  and  wholly  sufficient  to  account  for 
all  observed  cases.  In  every  instance  the  pre- 
viously existing  shape  of  the  leaf  must  have  de- 
cided whether  peltate  or  pitcher-like  leaves 
would  be  formed.  As  far  as  we  can  judge  pel- 
tate anomalies  are  quite  uninjurious,  while  as- 
cidia are  forms  which  must  impede  the  effect  of 
the  light  on  the  leaf,  as  they  conceal  quite  an 
important  part  of  the  upper  surface.  In  this 
way  it  is  easily  conceivable  that  peltate  leaves 
are  a  frequent  specific  character,  while  ascidia 
are  not,  as  they  only  appear  in  the  special  cases 
of  limited  adaptation,  as  in  the  instances  of  the 
so  called  pitcher-plants.    The  genera  Nepenthes, 


672  Mutations 

Sarracenia  and  some  others  are  very  well 
known  and  perhaps  even  the  bladderworts  or 
Utricularia  might  be  included  here. 

The  reproduction  of  specific  characters  by 
anomalous  ascidia  is  not  at  all  limited  to  the 
general  case  as  described  above.  More  minute 
details  may  be  seen  to  be  duplicated  in  the  same 
way.  Proofs  are  afforded  on  one  side  by  in- 
complete ascidia,  and  on  the  other  by  the  double 
cups. 

Incomplete  ascidia  are  those  of  the  Nepenthes. 
The  leaf  is  divided  into  three  parts,  a  blade,  a 
tendril  and  the  pitcher.  Or  in  other  words,  the 
limb  produces  a  tendril  at  its  summit,  by  means 
of  which  the  plant  is  enabled  to  fasten  itself  to 
surrounding  shrubs  and  to  climb  between  their 
branches.  But  the  end  of  this  tendril  bears  a 
well-formed  urn,  which  however,  is  produced 
only  after  the  revolving  and  grasping  move- 
ments of  the  tendril  have  been  made.  Some 
species  have  more  rounded  and  some  more 
elongated  ascidia  and  often  the  shape  is  seen  to 
change  with  the  development  of  the  stem.  The 
mouth  of  the  urn  is  strengthened  by  a  thick  rim 
and  covered  with  a  lid.  Numerous  curious  con- 
trivances in  these  structures  to  catch  ants  and 
other  insects  have  been  described,  but  as  they 
have  no  relation  to  our  present  discussion,  we 
shall  abstain  from  dealing  with  them. 


Taxonomic  Anomalies  673 

Likewise  we  must  refrain  from  a  consid- 
eration of  the  physiologic  qualities  of  the  ten- 
dril, and  confine  our  attention  to  the  combina- 
tion of  a  limb,  a  naked  midvein  and  an  ascidium. 
This  combination  is  to  be  the  basis  of  our  dis- 
cussion. It  is  liable  to  be  produced  all  of  a  sud- 
den. This  assertion  is  proved  by  its  occurrence 
as  a  varietal  mark  in  one  of  our  most  ordinary 
cultivated  plants.  It  is  the  group  known  as 
Croton,  belonging  to  the  genus  Codiaeum, 
A  variety  is  called  interruptum  and  another  ap- 
pendiculatiim^  and  these  names  both  relate  to 
the  interruption  of  the  leaves  by  a  naked  mid- 
vein.  The  leaves  are  seen  to  be  built  up  of  three 
parts.  The  lower  half  retains  the  aspect  of  a 
limb;  it  is  crowned  by  a  vein  without  lateral 
nerves  or  blade-like  expansions,  and  this  stalk 
in  its  turn  bears  a  short  limb  on  its  summit.  The 
base  of  this  apical  limb  exhibits  two  connate 
lobes,  forming  together  a  wide  cup  or  ascidium. 
It  should  be  stated  that  these  interruptum  varie- 
ties are  highly  variable,  especially  in  the  rela- 
tive size  of  the  three  principal  parts  of  the  leaf. 
Though  it  is  of  course  conceded  that  the  ascidium 
of  Nepenthes  has  many  secondary  devices 
which  are  lacking  in  Croton,  it  seems  hardly  al- 
lowable to  deny  the  possibility  of  an  analogous 
origin  for  both.  Those  of  the  Croton,  according 
to  our  knowledge  regarding  similar  cases,  must 


674  Mutations 

have  arisen  at  once,  and  hence  the  conclusion 
that  the  ascidia  of  Nepenthes  are  also  originally 
due  to  a  sudden  mutation.  Interrupted  leaves, 
with  an  ascidium  on  a  naked  prolongation  of  the 
midvein,  are  by  no  means  limited  to  the  Croton 
varieties.  As  stray  anomalies  they  have  often 
been  observed,  and  I  myself  had  the  oppor- 
tunity of  collecting  them  on  magnolia,  on  clover 
and  on  some  other  species.  They  are  additional 
evidence  in  support  of  the  explanation  given 
above. 

In  the  same  way  double  ascidia  may  be  made 
use  of  to  explain  the  foliar  cups  of  the  teasels 
and  some  other  plants,  as  for  instance,  some 
European  snakeroots  {Eryngium  maritimum 
and  E.  campestre),  or  the  floral  leaves  of  the 
honeysuckle.  The  leaves  on  the  stems  of  the 
teasels  are  disposed  in  pairs,  and  the  bases  of 
the  two  leaves  of  each  pair  are  connate  so  as 
to  constitute  large  cups.  We  have  already  men- 
tioned these  cups,  and  recall  them  in  the  present 
connection  to  use  them  as  a  prototype  of  the 
double  ascidia.  These  are  constituted  of  two  op- 
posite leaves,  accidentally  connated  at  their  base 
or  along  some  part  of  their  margins.  If  the 
leaves  are  sessile,  the  analogy  with  the  teasels 
is  complete,  as  shown,  for  instance,  in  a  case 
of  Cotyledon,  a  crassulaceous  plant  which  is 


Taxonomic  Anomalies  675 

known  to  produce  such  cups  from  time  to  time. 
They  are  narrower  than  those  of  the  teasel,  but 
this  depends,  as  we  have  seen  for  the  *'  one- 
leaved  ''  ascidium,  on  the  shape  of  the  original 
leaf.  In  other  respects  they  exactly  imitate  the 
teasel  cups,  showing  thereby  how  these  cups 
may  probably  have  originated. 

In  numerous  cases  of  anomalies  some  acci- 
dental structures  are  parallel  to  specific  char- 
acters, while  others  are  not,  being  obviously  in- 
jurious to  their  bearers.  So  it  is  also  with  the 
double  ascidia.  In  the  case  of  stalked  leaves 
the  two  opposite  stalks  must,  of  course,  consti- 
tute a  long  and  very  narrow  tube,  when  growing 
together.  This  tube  must  bear  at  its  summit 
the  conical  ascidium  produced  by  the  two  con- 
nate limbs.  At  its  base  however,  it  includes  the 
terminal  bud  of  the  stem,  and  frequently  the 
tube  is  so  narrow  as  to  impede  its  further  de- 
velopment. By  this  contrivance  the  double  as- 
cidium assumes  a  terminal  position.  Instances 
have  been  observed  on  magnolia,  in  Boehmeria 
and  in  other  cases. 

Flowers  on  leaves  are  of  rare  occurrence. 
Notwithstanding  this,  they  constitute  specific 
characters  in  some  instances,  accidental  anoma- 
lies in  others.  Helwingia  rusciflora  is  the  most 
curious  and  best  known  instance.  It  is  a 
little  shrub,  belonging  to  the  Cornaceae,  and 


676  Mutations 

has  broad  elliptical  undivided  leaves.  On 
the  middle  of  the  midvein  these  leaves  are  seen 
to  bear  small  clusters  of  flowers;  indeed  this 
is  the  only  place  where  flowers  are  produced. 
Each  cluster  has  from  13  - 15  flowers,  of  which 
some  are  staminate  and  borne  on  stalks,  while 
others  are  pistillate  and  nearly  sessile.  These 
flowers  are  small  and  of  a  pale  greenish  color 
and  yield  small  stone-fruits,  with  a  thin 
coating  of  pulpy  tissue.  As  the  name  indicates, 
this  mode  of  flowering  is  closely  similar  to  that 
of  Ruscus,  which  however,  does  not  bear  its 
flowers  and  berries  on  real  leaves,  but  on  leaf- 
like expansions  of  the  twigs.  Phyllonoma  nis- 
cifolia,  a  saxifragaceous  plant,  bears  the  same 
specific  name,  indicating  a  similar  origin  of  the 
flowers.  Other  instances  have  been  collected  by 
Casimir  de  Candolle,  but  their  number  is  very 

small. 

As  a  varietal  mark,  flowers  on  leaves  like- 
wise rarely  occur.  One  instance  however,  is 
very  remarkable,  and  we  have  already  dealt 
with  it,  when  treating  of  constant  varieties,  and 
of  the  lack  of  vicinism  in  the  case  of  species 
with  exclusive  self-fertilization. 

It  is  the  ''  Nepaul-barley  "  or  Hordeum  tri- 
furcatum.  The  leaves,  which  in  this  case  bear 
the  adventitious  flowers,  are  the  inner  scales  of 
the  spikelets,  and  not  on  green  leaves  as  in  the 


Taxonomic  Anomalies  677 

cases  already  alluded  to.  But  this  of  course 
makes  no  real  difference.  The  character  is 
variable  to  a  high  degree,  and  this  fact  indicates 
its  varietal  nature,  though  it  should  be  recalled 
that  at  least  with  the  Hehvingia,  the  majority  of 
the  leaves  are  destitute  of  flowers,  and  that  in 
this  way  some  degree  of  variability  is  present 
in  this  normal  case  too. 

All  in  all  there  are  three  sorts  of  ^'  Nepaul- 
barley.''  They  have  the  same  varietal  mark, 
but  belong  to  different  species  of  barley.  These 
are  differentiated  according  to  the  number  of 
the  rows  in  which  the  grains  are  seen  on  the 
spikes.  These  numbers  may  be  two,  four  or  six, 
giving  rise  to  the  specific  names  of  Hordeum  dis- 
tichum,  tetrastichum  and  hexastichum.  Whether 
these  three  varieties  are  of  independent,  but 
parallel  origin,  or  are  to  be  considered  as  due  to 
a  single  mutation  and  subsequent  crosses  is  not 
known,  all  of  them  being  of  ancient  origin. 
Historic  evidence  concerning  their  birth  is 
wholly  wanting.  From  analogy  it  would  seem 
probable  that  the  character  had  arisen  by  a  mu- 
tation in  one  of  the  three  named  species,  and 
had  been  transferred  to  others  by  means  of  ac- 
cidental crosses,  even  as  it  has  been  artificially 
transmitted  of  late  to  quite  a  number  of  other 
sorts.  But  however  admissible  this  conception 
may  seem,  there  is  of  course  no  real  objection 


678  Mutations 

to  the  assumption  of  independent  and  parallel 
mutations. 

For  the  purpose  of  a  comparison  with  the 
Helivingia  type  we  are  however,  not  at  all  con- 
cerned with  the  species  to  which  the  trifurca- 
tum  variety  belongs,  but  only  with  the  varietal 
mark  itself.  The  spikelets  may  be  one-,  two-  or 
three-flowered,  according  to  the  species.  If  we 
choose  for  further  consideration  the  hexasti- 
chum  type,  each  spikelet  produces  three  nor- 
mal flowers  and  afterwards  three  normal  grains. 
Morphologically  however,  the  spikelet  is  not 
homologous  to  those  parts  of  other  grasses 
which  have  the  same  name.  It  is  constituted  of 
three  real  spikelets,  and  thus  deserves  the  name 
of  a  triple  construction.  Each  of  these  three 
little  organs  has  its  normal  pair  of  outer  scales 
or  glumae.  These  are  linear  and  short,  ending 
in  a  long  and  narrow  spine.  Those  of  the  mid- 
dle-most spikelets  stand  on  its  outer  side,  while 
those  of  the  lateral  part  are  placed  transversely. 
In  this  way  they  form  a  kind  of  involucre 
around  the  central  parts.  The  latter  consist 
of  the  inner  and  outer  palets  or  scales,  each  two 
of  which  include  one  of  the  flowers.  The  outer 
palet  is  to  be  considered  as  the  metamorphosed 
leaf,  in  the  axil  of  which  the  flower  is  produced. 
In  the  common  sorts  of  barley  it  bears  a  long 
awn,  giving  thereby  its  typical  aspect  to  the 


Taxonomic  Anomalies  679 

whole  spike.  The  axillary  flower  is  protected  on 
the  opposite  side  by  a  two-keeled  inner  palet. 
Each  flower  exhibits  three  stamens  and  an 
ovary.  In  the  six-rowed  barley  all  the  three 
flowers  of  a  triple  spikelet  are  fertile,  and  each 
of  them  has  a  long  awn  on  the  top  of  the  outer 
palet.  But  in  the  two-rowed  species  only  the 
middle-most  flower  is  normal  and  has  an  awn, 
the  two  remaining  being  sterile  and  more  or  less 
rudimentary  and  with  only  very  short  awns. 
From  this  description  it  is  easily  seen  that  the 
species  of  barley  may  be  distinguished  from  one 
another,  even  at  a  casual  glance,  by  the  number 
of  the  rows  of  the  awns,  and  therefore  by  the 
shape  of  the  entire  spikes.  This  striking  fea- 
ture, however,  does  not  exist  in  the  ^^  Nepaul- 
barley."  The  awns  are  replaced  by  curiously 
shaped  appendices,  which  are  three-lobed.  The 
central  lobe  is  oblong  and  hollow,  and  forms  a 
kind  of  hood,  which  covers  a  small  supernumer- 
ary floret.  The  two  lateral  lobes  are  narrower, 
often  linear  and  extended  into  a  smaller  or 
longer  awn.  These  awns  are  mostly  turned 
away  from  the  center  of  the  spike.  The  central 
lobe  may  sometimes  bear  two  small  florets,  but 
ordinarily  only  one  is  to  be  found,  and  this  is 
often  incomplete,  having  only  one  or  two 
stamens,  or   is  different  in  some  other  way. 


680  Mutations 

These  narrow  lateral  lobes  heighten  the  abnor- 
mal aspect  of  the  whole  spike. 

They  are  only  produced  at  a  somewhat  ad- 
vanced stage  of  the  development  of  the  palet, 
are  united  to  one  another  and  to  the  central 
part  by  strong  veins,  which  form  transversal 
anastomoses  at  their  insertion.  The  length  of 
these  awns  is  very  variable,  and  this  quality  is 
perhaps  the  most  striking  of  the  whole  variety. 
Often  they  reach  only  1-2  mm.,  or  the  major- 
ity may  become  longer  and  attain  even  1  cm., 
while  here  and  there,  between  them,  longer  ones 
are  inserted,  extending  in  some  instances  even 
as  far  as  3  cm.  from  the  spike.  Their  trans- 
verse position  in  such  cases  is  strikingly  con- 
trasted with  the  ordinary  erect  type  of  the 
awns. 

These  lateral  lobes  are  to  be  regarded,  from 
the  morphologic  point  of  view,  as  differentiated 
parts  of  the  blade  of  the  leaf.  Before  they  are 
formed,  or  coincidently  with  the  beginning  of 
their  development,  the  summit  of  the  central 
lobe  becomes  hollow,  and  the  development  of 
the  supernumerary  flower  commences.  In  dif- 
ferent varieties,  and  especially  in  the  most  re- 
cent crosses  of  them,  this  development  is  ex- 
cessively variable. 

The  accidental  flower  arises  at  some  distance 
beneath  the  summit  of  the  scale,  on  its  middle 


Taxonomic  Anomalies  681 

vein.  The  development  begins  with  the  protru- 
sion of  a  little  scale,  and  the  flower  itself  is 
situated  beneath  this  scale,  and  is  to  be  pro- 
tected by  it  and  by  the  primary  scale,  but  is 
turned  upside  down  at  the  same  time.  Op- 
posite to  this  organ,  which  represents  the  outer 
palet  of  the  adventitious  flower,  two  little  swol- 
len bodies  are  evolved.  In  the  normal  flowers 
of  barley  and  other  grains  and  grasses  their 
function  is  to  open  the  flowers  by  swelling,  and 
afterwards  collapse  and  allow  them  to  close. 

In  the  adventitious  flowers  of  the  '^  Nepaul- 
barley,''  however,  this  function  is  quite  super- 
fluous. The  stamens  occur  in  varying  numbers ; 
typically  there  are  three,  but  not  rarely 
less,  or  more,  are  seen.  In  some  instances  the 
complete  double  whorl  of  six,  corresponding  to 
the  ancestral  monocotyledonous  type,  has  been 
found.  This  is  a  very  curious  case  of  sys- 
tematic atavism,  quite  analogous  to  the  Iris 
pallida  ahavia,  previously  alluded  to,  which 
likewise  has  six  stamens,  and  to  the  cases  given 
in  a  previous  lecture.  But  for  our  present  dis- 
cussion it  is  of  no  further  interest.  The  ovary 
is  situated  in  the  middle  of  the  flower,  and  in 
some  instances  two  have  been  observed.  This 
is  also  to  be  considered  as  a  case  of  atavism. 

All  these  parts  of  the  adventitious  flower  are 
more  or  less  subject  to  arrest  of  development 


682  Mutations 

in  a  later  stage.  They  may  even  sometimes  be- 
come abnormal.  Stamens  may  unite  into  pairs, 
or  carpels  bear  four  stigmas.  The  pollen-sacs 
are  as  a  rule  barren,  the  mother-cells  under- 
going atrophy,  while  normal  grains  are  seen  but 
rarely.  Likewise  the  ovaries  are  rudimentary, 
but  Wittmack  has  observed  the  occasional 
production  of  ripe  grains  from  these  abnormal 
florets. 

The  scale  is  seldom  seen  to  extend  any  far- 
ther upwards  than  the  supernumerary  flower. 
But  in  the  rare  instances  where  it  does  pro- 
long its  growth,  it  may  repeat  the  abnormality 
and  bear  a  second  floret  above  the  first.  This  of 
course  is  generally  much  weaker,  and  more  rudi- 
mentary. 

Raciborsky,  who  has  lately  given  a  full  and 
very  accurate  description  of  this  anomaly,  lays 
great  stress  upon  the  fact  that  it  is  quite  use- 
less. It  is  perhaps  the  most  obviously  useless 
structure  in  the  whole  vegetable  kingdom.  Not- 
withstanding this,  it  has  come  to  be  as  complete- 
ly hereditary  as  any  of  the  most  beautiful  adap- 
tations in  nature.  Therefore  it  is  one  of  the 
most  serious  objections  to  the  hypothesis  of 
slow  and  gradual  improvements  on  the  sole 
ground  of  their  usefulness.  The  struggle  for 
life  and  natural  selection  are  manifestly  in- 
adequate to  give  even  the  slightest  indication  of 


Taxonomic  Anomalies  683 

an  explanation  of  this  case.  It  is  simply  im- 
possible to  imagine  the  causes  that  might  have 
produced  such  a  character.  The  only  way  out 
of  this  difficulty  is  to  assume  that  it  has  arisen 
at  once,  in  its  present  apparently  differentiated 
and  very  variable  condition,  and  that,  being 
quite  uninjurious  and  since  it  does  not  decrease 
the  fertility  of  the  race,  it  has  never  been 
subjected  to  natural  selection,  and  so  has  saved 
itself  from  destruction. 

But  if  we  once  grant  the  probability  of  the 
origin  of  the  ' '  Nepaul-barley  "  by  a  sudden  mu- 
tation, we  obviously  must  assume  the  same  in 
the  case  of  the  Helwingia  and  other  normal  in- 
stances. In  this  way  we  gain  a  further  support 
for  our  assertion,  that  even  the  strangest 
specific  characters  may  have  arisen  suddenly. 

After  having  detailed  at  some  length  those 
proofs  which  seem  to  be  the  most  striking,  and 
which  had  not  been  previously  described  with 
sufficient  detail,  we  may  now  take  a  hasty  survey 
of  other  contingent  cases.  In  the  first  place  the 
cruciate  flowers  of  some  onagraceous  plants 
should  be  remembered.  Small  linear  petals  oc- 
cur as  a  specific  character  in  Oenothera  cru- 
ciata  of  the  Adirondacks,  but  have  been  seen  to 
arise  as  sudden  mutations  in  the  common  even- 
ing-primrose (0.  biennis)  in  Holland,  and  in  the 
willow-herb  (Epilobium  hirsutum)  in  England. 


684 


Mutations' 


Leaves  placed  in  whorls  of  three  are  very  rare. 
The  oleander,  jumper  and  some  few  other 
plants  have  ternate  whorls  as  a  specific  char- 
acter. As  an  anomaly,  ternate  whorls  are  far 
more  common,  and  perhaps  any  plant  with  op- 
posite leaves  may  from  time  to  time  produce 
them.  Races  rich  in  this  abnormality  are 
found  in  the  wild  state  in  the  yellow  loose- 
strife or  Lysimachia  vulgaris,  in  which  it  is 
a  very  variable  specific  character,  the  whorls 
varying  from  two  to  four  leaves.  In  the 
cultivated  state  it  is  met  with  in  the  myrtle 
or  Myrtus  communis,  where  it  has  come  to  be 
of  some  importance  in  Israelitic  ritual.  Crisped 
leaves  are  known  in  a  mallow,  Malva  crispa,  and 
as  a  variety  in  cabbages,  parsley,  lettuce  and 
others.  The  orbicular  fruits  of  Heeger's  shep- 
herd's purse  (Capsella  heegeri)  recall  similar 
fruits  of  other  cruciferous  genera,  as  for  in- 
stance, Camelina.  Screw-like  stems  with  wide 
spirals  are  specific  in  the  flower-stalks  of 
Cyclamen  and  Vallisneria,  varietal  in  Juncus 
effusus  spiralis  and  accidental  in  Scirpns  lacus- 
tris.  Dormant  buds  or  small  bulbs  in  inflo- 
rescences are  normal  for  wild  onions.  Polygo- 
num viviparum  and  others,  varietal  in  Poa 
alpina  vivipara  and  perhaps  in  Agave  vivi- 
para,  and  accidental  in  plantains  {Plant ago 
lanceolata),    Saxifraga    umbrosa    and    others. 


Taxonomic  Anomalies  685 

Cleft  leaves,  one  of  the  most  general  anomalies, 
are  typical  in  Boehmeria  hiloha.  The  adnation 
of  the  peduncles  of  the  inflorescences  to  the 
stem  is  typical  in  Solanum  and  accidental  in 
many  other  cases. 

It  seems  quite  superfluous  to  add  further 
proof.  It  is  a  very  general  phenomenon  that 
specific  characters  occur  in  other  genera  as 
anomalies,  and  under  such  circumstances  that 
the  idea  of  a  slow  evolution  on  the  ground  of 
utility  is  absolutely  excluded.  No  other  ex- 
planation remains  than  that  of  a  sudden  muta- 
tion, and  once  granted  for  the  abnormal  cases, 
this  explanation  must  obviously  likewise  be 
granted  for  the  analogous  specific  characters. 

Our  whole  discussion  shows  that  mutations, 
once  observed  in  definite  instances,  afford  the 
most  probable  basis  for  the  explanation  of  spe- 
cific characters  at  large. 


Lectuke  XXIV 

THE    HYPOTHESIS    OF   PERIODIC    MUTATIONS 

The  prevailing  belief  that  slow  and  gradual, 
nearly  invisible  changes  constitute  the  process 
of  evolution  in  the  animal  and  vegetable  king- 
dom, did  not  offer  a  strong  stimulus  for  experi- 
mental research.  No  appreciable  response  to 
any  external  agency  was  of  course  to  be  ex- 
pected. Responses  were  supposed  to  be  pro- 
duced, but  the  corresponding  outward  changes 
would  be  too  small  to  betray  themselves  to  the 
investigator. 

The  direct  observation  of  the  mutations  of 
the  evening-primrose  has  changed  the  whole 
aspect  of  the  problem  at  once.  It  is  no  longer 
a  matter  dealing  with  purely  hypothetical  con- 
ditions. Instead  of  the  vague  notions,  uncer- 
tain hopes,  and  a  priori  conceptions,  that  have 
hitherto  confused  the  investigator,  methods  of 
observation  have  been  formulated,  suitable  for 
the  attainment  of  definite  results,  the  general 
nature  of  which  is  already  known. 

To  my  mind  the  real  value  of  the  discovery 

686 


Periodic  Mutations  687 

of  the  mutability  of  the  evening-primrose  lies 
in  its  usefulness  as  a  guide  for  further  work. 
The  view  that  it  might  be  an  isolated  case,  lying 
outside  of  the  usual  procedure  of  nature,  can 
liardly  be  sustained.  On  such  a  supposition  it 
would  be  far  too  rare  to  be  disclosed  by  the 
investigation  of  a  small  number  of  plants  from 
a  limited  area.  Its  appearance  within  the  lim- 
ited field  of  inquiry  of  a  single  man  would  have 
been  almost  a  miracle. 

The  assumption  seems  justified  that  analo- 
gous cases  will  be  met  with,  perhaps  even  in 
larger  numbers,  when  similar  methods  of  ob- 
servation are  used  in  the  investigation  of  plants 
of  other  regions.  The  mutable  condition  may  <not 
be  predicated  of  the  evening-primroses  alone. 
It  must  be  a  universal  phenomenon,  although 
affecting  a  small  proportion  of  the  inhabitants 
of  any  region  at  one  time:  perhaps  not  more 
than  one  in  a  hundred  species,  or  perhaps  not 
more  than  one  in  a  thousand,  or  even  fewer  may 
be  expected  to  exhibit  it.  The  exact  proportion 
is  immaterial,  because  the  number  of  mutable 
instances  among  the  many  thousands  of  species 
in  existence  must  be  far  too  large  for  all  of 
them  to  be  submitted  to  close  scrutiny. 

It  is  evident  from  the  above  discussion  that 
next  in  importance  to  the  discovery  of  the  pro- 
totype of  mutation  is  the  formulation  of  meth- 


688  Mutations 

ods  for  bringing  additional  instances  to  light. 
These  methods  may  direct  effort  toward  two  dif- 
ferent modes  of  investigation.  We  may  search 
for  mutable  plants  in  nature,  or  we  may  hope 
to  induce  species  to  become  mutable  by  artificial 
methods.  The  first  promises  to  yield  results 
most  quickly,  but  the  scope  of  the  second  is 
much  greater  and  it  may  yield  results  of  far 
more  importance.  Indeed,  if  it  should  once  be- 
come possible  to  bring  plants  to  mutate  at  our 
will  and  perhaps  even  in  arbitrarily  chosen  di- 
rections, there  is  no  limit  to  the  power  we  may 
finally  hope  to  gain  over  nature. 

What  is  to  guide  us  in  this  new  line  of  work? 
Is  it  the  minute  inspection  of  the  features  of  the 
process  in  the  case  of  the  evening-primroses? 
Or  are  we  to  base  our  hopes  and  our  methods  on 
broader  conceptions  of  nature 's  laws  ?  Is  it  the 
systematic  study  of  species  and  varieties,  and 
the  biologic  inquiry  into  their  real  hereditary 
units?  Or  is  the  theory  of  descent  to  be  our 
starting-point?  Are  we  to  rest  our  conceptions 
on  the  experience  of  the  breeder,  or  is  perhaps 
the  geologic  pedigree  of  all  organic  life  to  open 
to  us  better  prospects  of  success? 

The  answer  to  all  such  questions  is  a  very 
simple  one.  All  possibilities  must  be  considered, 
and  no  line  of  investigation  ignored.  For  my- 
self I  have  based  my  field-researches  and  my 


Periodic  Mutations  689 

testing  of  native  plants  on  the  hypothesis  of 
unit-characters  as  deduced  from  Darwin's 
Pangenesis.  This  conception  led  to  the  expec- 
tation of  two  different  kinds  of  variability,  one 
slow  and  one  sudden.  The  sudden  ones  known 
at  the  time  were  considered  as  sports,  and 
seemed  limited  to  retrograde  changes,  or  to 
cases  of  minor  importance.  The  idea  that 
sudden  steps  might  be  taken  as  the  principal 
method  of  evolution  could  be  derived  from  the 
hypothesis  of  unit-characters,  but  the  evidence 
might  be  too  remote  for  a  starting  point  for  ex- 
perimental investigation. 

The  success  of  my  test  has  given  proof  to  the 
contrary.  Hence  the  assertion  that  no  evidence 
is  to  be  considered  as  inadequate  for  the  pur- 
pose under  discussion.  Sometime  a  method  of 
discovering,  or  of  producing,  mutable  plants 
may  be  found,  but  until  this  is  done,  all  facts  of 
whatever  nature  or  direction  must  be  made  use 
of.  A  very  slight  indication  may  change  for- 
ever the  whole  aspect  of  the  problem. 

The  probabilities  are  now  greatly  in  favor  of 
our  finding  out  the  causes  of  evolution  by 
a  close  scrutiny  of  what  really  happens  in  na- 
ture. A  persistent  study  of  the  physiologic 
factors  of  this  evolution  is  the  chief  condition 
of  success.  To  this  study  field-observations 
may  contribute  as  well  as  direct  experiments. 


690  Mutations 

microscopical  investigations  as  well  as  extended 
pedigree-cultures.  The  cooperation  of  many 
workers  is  required  to  cover  the  field.  Some- 
where no  doubt  the  desired  principle  lies  hid- 
den, but  until  it  is  discovered,  all  methods  must 
be  tried. 

With  this  conception  as  the  best  starting- 
point  for  further  investigation,  we  may  now 
make  a  brief  survey  of  the  other  phase  of  the 
problem.  We  shall  try  to  connect  our  observa- 
tions on  the  evening-primroses  with  the  theory 
of  descent  at  large. 

We  start  with  two  main  facts.  One  is  the 
mutability  of  Lamarck's  primrose,  and  the  sec- 
ond is  the  immutable  condition  of  quite  a  num- 
ber of  other  species.  Among  them  are  some 
of  its  near  allies,  the  common  and  the  small- 
flowered  evening-primrose,  or  Oenothera  bien- 
nis and  0.  muricata. 

From  these  facts,  a  very  important  question 
arises  in  connection  with  the  theory  of  descent. 
Is  the  mutability  of  our  evening-primroses  tem- 
porary, or  is  it  a  permanent  condition?  A  dis- 
cussion of  this  problem  will  give  us  the  means  of 
reaching  a  definite  idea  as  to  the  scope  of  our 
inquiries. 

Let  us  consider  the  present  first.  If  mutabil- 
ity is  a  permanent  condition,  it  has  of  course  no 
bednninsr,    and   moreover   is   not   due   to   the 


Periodic  Mutations  691 

agency  of  external  circumstances.  Should  this 
be  granted  for  the  evening-primrose,  it  would 
have  to  be  predicated  for  other  species  found  in 
a  mutable  state.  Then,  of  course,  it  would  be 
useless  to  investigate  the  causes  of  mutability 
at  large,  and  we  should  have  to  limit  ourselves 
to  the  testing  of  large  numbers  of  plants  in 
order  to  ascertain  which  are  mutable  and 
which  not. 

If,  on  the  other  hand,  mutability  is  not  a  per- 
manent feature,  it  must  once  have  had  a  begin- 
ning, and  this  beginning  itself  must  have  had  an 
external  cause.  The  amount  of  mutability  and  its 
possible  directions  may  be  assumed  to  be  due  to 
internal  causes.  The  determination  of  the  mo- 
ment at  which  they  will  become  active  can  never 
be  the  result  of  internal  causes.  It  must  be  as- 
signed to  some  external  factor,  and  as  soon  as 
this  is  discovered  the  way  for  experimental  in- 
vestigation is  open. 

In  the  second  place  we  must  consider  the  past. 
On  the  supposition  of  permanency  all  the  ances- 
tors of  the  evening-primrose  must  have  been 
mutable.  By  the  alternative  view  mutability 
must  have  been  a  periodic  phenomenon,  produc- 
ing at  times  new  qualities,  and  at  other  times 
leaving  the  plants  unchanged  during  long  suc- 
cessions of  generations.  The  present  mutable 
state  must  then  have  been  preceded  by  an  im- 


692  Mutations 

mutable  condition,  but  of  course  thousands  of 
mutations  must  have  been  required  to  produce 
the  evening-primroses  from  their  most  remote 
ancestors. 

If  we  take  the  species  into  consideration 
that  are  not  mutable  at  present,  we  may  ask 
how  we  are  to  harmonize  them  with  each  of 
the  two  theories  proposed.  If  mutability  is 
permanent,  it  is  manifest  that  the  whole  pedi- 
gree of  the  animal  and  vegetable  kingdom  is  to 
be  considered  as  built  up  of  main  mutable  lines, 
and.  that  the  thousands  of  constant  species  can 
only  be  taken  to  represent  lateral  branches  of 
the  genealogic  tree. 

These  lateral  branches  would  have  lost  the 
capacity  of  mutating,  possessed  by  all  their  an- 
cestors. And  as  the  principle  of  the  hypothesis 
under  discussion  does  not  allow  a  resumption  of 
this  habit,  they  would  be  doomed  to  eternal  con- 
stancy until  they  finally  die  out.  Loss  of  muta- 
bility, under  this  conception,  means  loss  of  the 
capacity  for  all  further  development.  Only 
those  lines  of  the  main  pedigree  which  have 
retained  this  capacity  would  have  a  future ;  all 
others  would  die  out  without  any  chance  of  pro- 
gression. 

If,  on  the  other  hand,  mutability  is  not  perma- 
nent, but  a  periodic  condition,  all  lines  of  the 
genealogic  tree  must  be  assumed  to  show  alter- 


Periodic  Mutations  693 

natively  mutating  and  constant  species.  Some 
lines  may  be  mutating  at  the  present  moment; 
others  may  momentarily  be  constant.  The  mu- 
tating lines  will  probably  sooner  or  later  revert 
to  the  inactive  state,  while  the  powers  of  de- 
velopment now  dormant  may  then  become  awak- 
ened on  other  branches. 

The  view  of  permanency  represents  life  as 
being  surrounded  with  unavoidable  death,  the 
principle  of  periodicity,  on  the  contrary,  fol- 
lows the  idea  of  resurrection,  granting  the 
possibility  of  future  progression  for  all  living 
beings.  At  the  same  time  it  yields  a  more  hope- 
ful prospect  for  experimental  inquiry. 

Experience  must  decide  between  the  two  main 
theories.  It  demonstrates  the  existence  of  poly- 
morphous genera,  such  as  Draba  and  Viola  and 
hundreds  of  others.  They  clearly  indicate  a 
previous  state  of  mutability.  Their  systematic 
relation  is  exactly  what  would  be  expected,  if 
they  were  the  result  of  such  a  period.  Perhaps 
mutability  has  not  wholly  ceased  in  them,  but 
might  be  found  to  survive  in  some  of  their  mem- 
bers. Such  very  rich  genera  however,  are  not 
the  rule,  but  are  exceptional  cases,  indicating 
the  rarity  of  powerful  mutative  changes. 

On  the  other  hand,  species  may  remain  in  a 
state  of  constancy  during  long,  apparently  dur- 
ing indefinite,  ages. 


694 


Mutations 


Many  facts  plead  in  favor  of  the  constancy 
of  species.  This  principle  has  always  been 
recognized  by  systematists.  Temporarily  the 
current  form  of  the  theory  of  natural  selec- 
tion has  assumed  species  to  be  inconstant,  ever 
changing  and  continuously  being  improved  and 
adapted  to  the  requirements  of  the  life-condi- 
tions. The  followers  of  the  theory  of  descent 
believed  that  this  conclusion  was  unavoidable, 
and  were  induced  to  deny  the  manifest  fact  that 
species  are  constant  entities.  The  mutation 
theory  gives  a  clew  to  the  final  combination  of 
the  two  contending  ideas.  Reducing  the  change- 
ability of  the  species  to  distinct  and  probably 
short  periods,  it  at  once  explains  how  the 
stability  of  species  perfectly  agrees  with  the 
principle  of  descent  through  modification. 

On  the  other  hand,  the  hypothesis  of  mutative 
periods  is  by  no  means  irreconcilable  with  the 
observed  facts  of  constancy.  Such  casual 
changes  can  be  proved  by  observations  such  as 
those  upon  the  evening-primrose,  but  it  is  ob- 
vious that  a  disproof  can  never  be  given.  The 
principle  grants  the  present  constancy  of  the 
vast  majority  of  living  forms,  and  only  claims 
the  exceptional  occurrence  of  definite  changes. 

Proofs  of  the  constancy  of  species  have  been 
given  in  different  ways.  The  high  degree  of 
similarity  of  the  individuals  of  most  of  our 


Periodic  Mutations  695 

species  has  never  been  denied.  It  is  observed 
throughout  extended  localities,  and  during  long 
series  of  years.  Other  proofs  are  afforded  by 
those  plants  which  have  been  transported  to  dis- 
tant localities  some  time  since,  but  do  not  ex- 
hibit any  change  as  a  result  of  this  migration. 
Widely  dispersed  plants  remain  the  same 
throughout  their  range,  provided  that  they  be- 
long to  a  single  elementary  species.  Many 
species  have  been  introduced  from  America  into 
Europe  and  have  spread  rapidly  and  widely. 
The  Canadian  horsetail  {Erigeron  canadensis) , 
the  evening-primrose  and  many  other  instances 
could  be  given.  They  have  not  developed  any 
special  European  features  after  their  introduc- 
tion. Though  exposed  to  other  environmental 
conditions  and  to  competition  with  other  spe- 
cies, they  have  not  succeeded  in  developing 
a  new  character.  Such  species  as  proved  ade- 
quate to  the  new  environment  have  succeeded, 
while  those  which  did  not  have  succumbed. 

Much  farther  back  is  the  separation  of  the 
species  which  now  live  both  in  arctic  regions 
and  on  the  summits  of  our  highest  mountain- 
tops.  If  we  compare  the  alpine  flora  with  the 
arctic  plants,  a  high  degree  of  similarity  at  once 
strikes  us.  Some  forms  are  quite  identical; 
others  are  slightly  different,  manifestly  repre- 
senting elementary   species  of  the   same  sys- 


696  Mutations 

tematic  type.  Still  others  are  more  distant  or 
even  belong  to  different  genera.  The  latter, 
and  even  the  diverging,  though  nearly  allied, 
elementary  species,  do  not  yield  adequate  evi- 
dence in  any  direction. 

They  may  as  well  have  lived  together   in 
the  long  ages  before  the  separation  of  the  now 
widely  distant  floras,  or  have  sprung  from  a 
common  ancestor  living  at  that  time,  and  subse- 
quently have  changed  their  habits.     After  ex- 
cluding these  unreliable  instances,  a  good  num- 
ber of  species  remain,  which  are  quite  the  same 
in  the  arctic  and  alpine  regions  and  on  the  sum- 
mits of  distant  mountain-ranges.     As  no  trans- 
portation over  such  large  distances  can  have 
brought  them  from  one  locality  to  the  other,  no 
other  explanation  is  left  than  that  they  have 
been  wholly  constant  and  unchanged  ever  since 
the  glacial  period  which  separated  them.     Ob- 
viously they  must  have  been  subjected  to  widely 
changing  conditions.     The  fact  of  their  stability 
through  all  these  outward  changes  is  the  best 
proof  that  the  ordinary  external  conditions  do 
not  necessarily  have  an  influence  on  specific  evo- 
lution.    They  may  have  such  a  result  in  some 
instances,  in  others  they  obviously  have  not. 
Many  arctic  forms  bearing  the  specific  name  of 
alpinus  justify  this  conclusion.     Astragalus  al- 
pinus,  Phleum  alpinum,  Hieracium  alpinum  and 


Periodic  Mutatio.ns  697 

others  from  the  northern  parts  of  Norway  may 
be  cited  as  examples. 

Thus  Primula  imperialis  has  been  found 
in  the  Himalayas,  and  many  other  plants  of  the 
high  mountains  of  Java,  Ceylon  and  north- 
ern India  are  identical  forms.  Some  species 
from  the  Cameroons  and  from  Abyssinia  have 
been  found  on  the  mountains  of  Madagascar. 
Some  peculiar  Australian  types  are  represented 
on  the  summit  of  Kini  Balu  in  Borneo.  None  of 
these  species,  of  course,  are  found  in  the  inter- 
vening lowlands,  and  the  only  possible  explana- 
tion of  their  identity  is  the  conception  of  a  com- 
mon post-glacial  origin,  coupled  with  complete 
stability.  This  stability  is  all  the  more  remark- 
able as  nearly  allied  but  slightly  divergent 
forms  have  also  been  reported  from  almost 
all  of  these  localities.  Other  evidence  is 
obtained  by  the  comparison  of  ancient  plants 
with  their  living  representatives.  The  re- 
mains in  tombs  of  ancient  Egypt  have  al- 
ways afforded  strong  support  of  the  views  of 
the  adherents  of  the  theory  of  stability,  and  to 
my  mind  they  still  do  so.  The  cereals  and  fruits 
and  even  the  flowers  and  leaves  in  the  funeral 
wreaths  of  Rameses  and  Amen-Hotep  are  the 
same  that  are  still  now  cultivated  in  Egypt. 
Nearly  a  hundred  or  more  species  have  been 
identified.     Flowers  of  Acacia,  leaves  of  Mimu- 


698 


Mutations 


sops,  petals  of  Nymphaea  may  be  cited  as  in- 
stances, and  they  are  as  perfectly  preserved  as 
the  best  herbarium-specimens  of  the  present 
time.  The  petals  and  stamens  retain  their  orig- 
inal colors,  displaying  them  as  brightly  as  is 
consistent  with  their  dry  state. 

Paleontologic  evidence  points  to  the  same 
conclusion.  Of  course  the  remains  are  incom- 
plete, and  rarely  adequate  for  a  close  compari- 
son. The  range  of  fluctuating  variability  should 
be  examined  first,  but  the  test  of  elementary 
species  given  by  their  constancy  from  seed  can- 
not, of  course,  be  applied.  Apart  from  these 
difficulties,  paleontologists  agree  in  recognizing 
the  very  great  age  of  large  numbers  of  species. 
It  would  require  a  too  close  survey  of  geologic 
facts  to  go  into  details  on  this  point.  Suffice  it 
to  say  that  in  more  recent  Tertiary  deposits 
many  species  have  been  identified  with  living 
forms.  In  the  Miocene  period  especially,  the 
similarity  of  the  types  of  phanerogamic  plants 
with  their  present  offspring,  becomes  so  striking 
that  in  a  large  number  of  cases  specific  distinc- 
tions rest  in  greater  part  on  theoretical  con- 
ceptions rather  than  on  real  facts.  For  a  long 
time  the  idea  prevailed  that  the  same  species 
could  not  have  existed  through  more  than  one 
geologic  period.  Many  distinctions  founded 
on  this  belief  have  since  had  to  be  abandoned. 


Periodic  Mutations  699 

Species  of  algae  belonging  to  the  well-pre- 
served group  of  the  diatoms,  are  said  to  have 
remained  unchanged  from  the  Carboniferous 
period  up  to  the  present  time. 

Summing  up  the  results  of  this  very  hasty 
survey,  we  may  assert  that  species  remain  un- 
changed for  indefinite  periods,  while  at  times 
they  are  in  the  alternative  condition.  Then  at 
once  they  produce  new  forms  often  in  large 
numbers,  giving  rise  to  swarms  of  subspecies. 
All  facts  point  to  the  conclusion  that  these  pe- 
riods of  stability  and  mutability  alternate  more 
or  less  regularly  with  one  another.  Of  course 
a  direct  proof  of  this  view  cannot,  as  yet,  be 
given,  but  this  conclusion  is  forced  upon  us  by 
a  consideration. of  known  facts  bearing  on  the 
principle  of  constancy  and  evolution. 

If  we  are  right  in  this  general  conception,  we 
may  ask  further,  what  is  to  be  the  exact  place 
of  our  group  of  new  evening-primroses  in  this 
theory?  In  order  to  give  an  adequate  answer, 
we  must  consider  the  whole  range  of  the  obser- 
vations from  a  broader  point  of  view.  First  of 
all  it  is  evident  that  the  real  mutating  period 
must  be  assumed  to  be  much  longer  than  the 
time  covered  by  my  observations.  Neither  the 
beginning  nor  the  end  have  been  seen.  It  is 
quite  obvious  that  Oenothe^^a  lamarchiana 
was    in    a    mutating    condition    when    I    first 


700  Mutations 

saw  it,  seventeen  years  ago.  How  long  had 
it  been  so!  Had  it  commenced  to  mutate  after 
its  introduction  into  Europe,  some  time  ago,  or 
was  it  already  previously  in  this  state!  It 
is  as  yet  impossible  to  decide  this  point.  Per- 
haps the  mutable  state  is  very  old,  and  dates 
from  the  time  of  the  first  importation  of  the 
species  into  Europe. 

Apart  from  all  such  considerations  the  period 
of  the  direct  observations,  and  the  possible 
duration  of  the  mutability  through  even  more 
than  a  century,  would  constitute  only  a  moment, 
if  compared  with  the  whole  geologic  time. 
Starting  from  this  conception  the  pedigree  of 
our  mutations  must  be  considered  as  only  one 
small  group.  Instead  of  figuring  a  fan  of  mu- 
tants for  each  year,  we  must  condense  all  the 
succeeding  swarms  into  one  single  fan,  as  might 
be  done  also  for  Draha  verna  and  other  poly- 
morphous species.  In  Oenothera  the  main  stem 
is  prolonged  upwards  beyond  the  fan;  in  the 
others  the  main  stem  is  lacking  or  at  least 
undiscernible,  but  this  feature  manifestly  is  only 
of  secondary  importance.  We  might  even  pre- 
fer the  image  of  a  fan,  adjusted  laterally  to 
a  stem,  which  itself  is  not  interrupted  by  this 
branch. 

On  this  principle  two  further  considerations 
are  to  be  discussed.     First  the  structure  of  the 


Periodic  Mutations  701 

fan  itself,  and  secondly  the  combination  of  suc- 
ceeding fans  into  a  common  genealogic  tree. 

The  composition  of  the  fan  as  a  whole  in- 
cludes more  than  is  directly  indicated  by  the 
facts  concerning  the  birth  of  new  species.  They 
arise  in  considerable  quantities,  and  each  of 
them  in  large  numbers  of  individuals,  either  in 
the  same  or  in  succeeding  years.  This  multiple 
origin  must  obviously  have  the  effect  of 
strengthening  the  new  types,  and  of  heightening 
their  chances  in  the  struggle  for  life.  Arising 
in  a  single  specimen  they  would  have  little 
chance  of  success,  since  in  the  field  among  thou- 
sands of  seeds  perhaps  one  only  survives  and 
attains  complete  development.  Thousands  or 
at  least  hundreds  of  mutated  seeds  are  thus  re- 
quired to  produce  one  mutated  individual,  and 
then,  how  small  are  its  chances  of  surviving! 
The  mutations  proceed  in  all  directions,  as  I 
have  pointed  out  in  a  former  lecture.  Some  are 
useful,  others  might  become  so  if  the  circum- 
stances were  accidentally  changed  in  definite 
directions,  or  if  a  migration  from  the  original 
locality  might  take  place.  Many  others  are 
without  any  real  worth,  or  even  injurious. 
Harmless  or  even  slightly  useless  ones  have 
been  seen  to  maintain  themselves  in  the  field 
during  the  seventeen  years  of  my  research,  as 
proved    by    Oenothera    laevifolia    and    Oeno- 


702  Mutations 

thera  brevistylis.     Most  of  the  others  quickly 
disappear. 

This  failure  of  a  large  part  of  the  productions 
of  nature  deserves  to  be  considered  at  some 
length.  It  may  be  elevated  to  a  principle,  and 
may  be  made  use  of  to  explain  many  diffi- 
cult points  of  the  theory  of  descent.  If,  in 
order  to  secure  one  good  novelty,  nature  must 
produce  ten  or  twenty  or  perhaps  more  bad 
ones  at  the  same  time,  the  possibility  of  im- 
provements coming  by  pure  chance  must  be 
granted  at  once.  All  hypotheses  concerning  the 
direct  causes  of  adaptation  at  once  become  su- 
perfluous, and  the  great  principle  enunciated  by 
Darwin  once  more  reigns  supreme. 

In  this  way  too,  the  mutation-period  of  the 
evening-primrose  is  to  be  considered  as  a  proto- 
type. Assuming  it  as  such  provisionally,  it  may 
aid  us  in  arranging  the  facts  of  descent  so  as  to 
allow  of  a  deeper  insight  and  a  closer  scrutiny. 
All  swarms  of  elementary  species  are  the  re- 
mains of  far  larger  initial  groups.  All  species 
containing  only  a  few  subspecies  may  be  sup- 
posed to  have  thrown  off  at  the  outset  far  more 
numerous  lateral  branches,  out  of  which  how- 
ever, the  greater  part  have  been  lost,  being 
unfit  for  the  surrounding  conditions.  It  is 
the  principle  of  the  struggle  for  life  between  ele- 
mentary species,  followed  by  the  survival  of  the 


Periodic  Mutations  703 

fittest,  the  law  of  the  selection  of  species,  which 
we  have  already  laid  stress  upon  more  than 
once. 

Our  second  consideration  is  also  based  upon 
the  frequent  repetition  of  the  several  mutations. 
Obviously  a  common  cause  must  prevail.  The 
faculty  of  producing  nanella  or  lata  remains  the 
same  through  all  the  years.  This  faculty  must 
be  one  and  the  same  for  all  the  hundreds  of  mu- 
tative productions  of  the  same  form.  When 
and  how  did  it  originate  I  At  the  outset  it  must 
have  been  produced  in  a  latent  condition,  and 
even  yet  it  must  be  assumed  to  be  continuously 
present  in  this  state,  and  only  to  become  active 
at  distant  intervals.  But  it  is  manifest  that 
the  original  production  of  the  characters  of 
Oenothera  gigas  was  a  phenomenon  of  far  great- 
er importance  than  the  subsequent  accidental 
transition  of  this  quality  into  the  active  state. 
Hence  the  conclusion  that  at  the  beginning  of 
each  series  of  analogous  mutations  there  must 
have  been  one  greater  and  more  intrinsic  mu- 
tation, which  opened  the  possibility  to  all  its 
successors.  This  was  the  origination  of  the 
new  character  itself,  and  it  is  easily  seen  that 
this  incipient  change  is  to  be  considered  as  the 
real  one.  All  others  are  only  its  visible  ex- 
pressions. 

Considering  the  mutative  period  of  our  even- 


704  Mutations 

ing-primrose  as  one  unit-stride  section  in  the 
great  genealogic  tree,  this  period  includes  two 
nearly  related,  but  not  identical  changes.  One 
is  the  production  of  new  specific  characters  in 
the  latent  condition,  and  the  other  is  the  bring- 
ing of  them  to  light  and  putting  them  into  active 
existence.  These  two  main  factors  are  conse- 
quently to  be  assumed  in  all  hypothetic  concep- 
tions of  iDrevious  mutative  periods. 

Are  all  mutations  to  be  considered  as  limited 
to  such  periods?  Of  course  not.  Stray  muta- 
tions may  occur  as  well.  Our  knowledge  con- 
cerning this  point  is  inadequate  for  any  definite 
statement.  Swarms  of  variable  species  are 
easily  recognized,  if  the  remnants  are  not  too 
few.  But  if  only  one  or  two  new  species  have 
survived,  how  can  we  tell  whether  they  have 
originated  alone  or  together  with  others.  This 
difficulty  is  still  more  pronounced  in  regard  to 
paleontologic  facts,  as  the  remains  of  geologic 
swarms  are  often  found,  but  the  absence  of 
numerous  mutations  can  hardly  be  proved  in 
anv  case. 

I  have  more  than  once  found  occasion  to  lay 
stress  on  the  importance  of  a  distinction  be- 
tween progressive  and  retrograde  mutations  in 
previous  lectures.  All  improvement  is,  of 
course,  by  the  first  of  these  modes  of  evolution, 
but  apparent  losses  of  organs  or  qualities  are 


Periodic  Mutations  705 

perhaps  of  still  more  universal  occurrence.  Pro- 
gression and  regression  are  seen  to  go  hand  in 
hand  everywhere.  No  large  group  and  proba- 
bly even  no  genus  or  large  species  has  been 
evolved  without  the  joint  agency  of  these  two 
great  principles.  In  the  mutation-period  of  the 
evening-primroses  the  observed  facts  give  direct 
support  to  this  conclusion,  since  some  of  the 
new  species  proved,  on  closer  inspection,  to  be 
retrograde  varieties,  while  others  manifestly 
owe  their  origin  to  progressive  steps.  Such 
steps  may  be  small  and  in  a  wrong  direction; 
notwithstanding  this  they  may  be  due  to  the 
acquisition  of  a  wholly  new  character  and  there- 
fore belong  to  the  process  of  progression  at 
large. 

Between  them  however,  there  is  a  definite 
contrast,  which  possibly  is  in  intimate  connec- 
tion with  the  question  of  periodic  and  stray  mu- 
tations. Obviously  each  progressive  change  is 
dependent  upon  the  production  of  a  new  charac- 
ter, for  whenever  this  is  lacking,  no  such  muta- 
tion is  possible.  Retrograde  changes,  on  the 
other  hand,  do  not  require  such  elaborate  pre- 
liminary work.  Each  character  may  be  con- 
verted into  the  latent  condition,  and  for  all  we 
know,  a  special  preparation  for  this  purpose  is 
not  at  all  necessary.  It  is  readily  granted  that 
such  special  preparation  may  occur,  because  the 


706  Mutations 

great  numbers  in  wliich  onr  dwarf  variety  of  the 
Oenothera  are  yearly  produced  are  suggestive 
of  such  a  condition.  On  the  other  hand,  the 
laevifolia  and  hrevistylis  mutations  have  not 
been  repeated,  at  least  not  in  a  visible  way. 

From  this  discussion  we  may  infer  that  it  is 
quite  possible  that  a  large  part  of  the  progres- 
sive changes,  and  a  smaller  part  of  the  retro- 
grade mutations,  are  combined  into  groups,  ow- 
ing their  origin  to  common  external  agencies. 
The  periods  in  which  such  groups  occur  would 
constitute  the  mutative  periods.  Besides  them 
the  majority  of  the  retrograde  changes  and 
some  progressive  steps  might  occur  separately, 
each  being  due  to  some  special  cause.  De- 
gressive mutations,  or  those  which  arise  by 
the  return  of  latent  qualities  to  activity,  would 
of  course  belong  with  the  latter  group. 

This  assumption  of  a  stray  and  isolated  pro- 
duction of  varieties  is  to  a  large  degree  sup- 
ported by  experience  in  horticulture.  Here 
there  are  no  real  swarms  of  mutations.  Sud- 
den leaps  in  variability  are  not  rare,  but  then 
they  are  due  to  hybridization.  Apart  from  this 
mixture  of  characters,  varieties  as  a  rule  appear 
separately,  often  with  intervals  of  dozens  of 
years,  and  without  the  least  suggestion  of  a  com- 
mon cause.  Tt  is  quite  superfluous  to  go  into 
details,  as  we  have  dealt  with  the  horticultural 


Periodic  Mutations  707 

mutations  at  sufficient  length  on  a  previous  oc- 
casion. Only  the  instance  of  the  peloric  toad- 
flax might  be  recalled  here,  because  the  historic 
and  geographic  evidence,  combined  with  the  re- 
sults of  our  pedigree-experiment,  plainly  show 
that  peloric  mutations  are  quite  independent  of 
any  periodic  condition.  They  may  occur  any- 
where in  the  wide  range  of  the  toad-flax,  and  the 
capacity  of  repeatedly  producing  them  has 
lasted  some  centuries  at  least,  and  is  perhaps 
even  as  old  as  the  species  itself. 

Leaving  aside  such  stray  mutations,  we  may 
now  consider  the  probable  constitution  of  the 
great  lines  of  the  genealogic  tree  of  the  evening- 
primroses,  and  of  the  whole  vegetable  and  ani- 
mal kingdom  at  large.  The  idea  of  drawing  up 
a  pedigree  for  the  chief  groups  of  living  organ- 
isms is  originally  due  to  Haeckel,  who  used  this 
graphic  method  to  support  the  Darwinian  the- 
ory of  descent.  Of  course,  HaeckePs  genealogic 
trees  are  of  a  purely  hypothetic  nature,  and  have 
no  other  purpose  than  to  convey  a  clear  concep- 
tion of  the  notion  of  descent,  and  of  the  great 
lines  of  evolution  at  large.  Obviously  all  de- 
tails are  subject  to  doubt,  and  many  have  ac- 
cordingly been  changed  by  his  successors.  These 
changes  may  be  considered  as  partial  improve- 
ments, and  the  somewhat  picturesque  form  of 
HaeckePs  pedigree  might  well  be  replaced  by 


p 

708  Mutations  I 

more  simple  plans.  But  the  changes  have  by  no 
means  removed  the  doubts,  nor  have  they  been 
able  to  supplant  the  general  impression  of  dis- 
tinct groups,  united  by  broad  lines.  This 
feature  is  very  essential,  and  it  is  easily  seen  to 
correspond  with  the  conception  of  swarms,  as 
we  have  deduced  it  from  the  study  of  the  lesser 
groups. 

Genealogic  trees  are  the  result  of  comparative 
studies ;  they  are  far  removed  from  the  results 
of  experimental  inquiry  concerning  the  origin  of 
species.  What  are  the  links  which  bind  them 
together?  Obviously  they  must  be  sought  in 
the  mutative  periods,  which  have  immediately 
preceded  the  present  one.  In  the  case  of  the 
evening-primrose  the  systematic  arrangement 
of  the  allied  species  readily  guides  us  in  the  de- 
limitations of  such  periods.  For  manifestly 
the  species  of  the  large  genus  of  Oenothera  are 
grouped  in  swarms,  the  youngest  or  most  recent 
of  which  we  have  under  observation.  Its  imme- 
diate predecessor  must  have  been  the  subgenus 
Onagra,  which  is  considered  by  some  authors  as 
consisting  of  a  single  systematic  species,  Oenoth- 
era biennis.  Its  multifarious  forms  point  to  a 
common  origin,  not  only  morphologically  but 
also  historically.  Following  this  line  backward 
or  downward  we  reach  another  apparent  muta- 
tion-period,   which    includes    the    origin      of 


Periodic  Mutations  709 

the  group  called  Oenothera,  with  a  large  num- 
ber of  species  of  the  same  general  type  as  the 
Onagra-forms.  Still  farther  downward  comes 
the  old  genus  Oenothera  itself,  with  numerous 
subgenera  diverging  in  sundry  characters  and 
directions. 

Proceeding  still  farther  we  might  easily  con- 
struct a  main  stem  with  numerous  succeeding 
fans  of  lateral  branches,  and  thus  reach,  from 
our  new  empirical  point  of  view,  the  theoretical 
conclusion  already  formulated. 

Paleontologic  facts  readily  agree  with  this 
conception.  The  swarms  of  species  and  va- 
rieties are  found  to  succeed  one  another  like  so 
many  stories.  The  same  images  are  repeated, 
and  the  single  stories  seem  to  be  connected  by 
the  main  stems,  which  in  each  tier  produce  the 
whole  number  of  allied  forms.  Only  a  few  pre- 
vailing lines  are  prolonged  through  numerous 
geologic  periods;  the  vast  majority  of  the  lat- 
eral branches  are  limited  each  to  its  own  storey. 
It  is  simply  the  extension  of  the  pedigree  of 
the  evening-primroses  backward  through  ages, 
with  the  same  construction  and  the  same  lead- 
ing features.  There  can  be  no  doubt  that  we 
are  quite  justified  in  assuming  that  evolution 
has  followed  the  same  general  laws  through  the 
whole  duration  of  life  on  earth.  Only  a  mo- 
ment of  their  lifetime  is  disclosed  to  us,  but  it 


710  Mutations 

is  quite  sufficient  to  enable  us  to  discern  the 
laws  and  to  conjecture  the  outlines  of  the  whole 
scheme  of  evolution. 

A  grave  objection  which  has  often,  and 
from  the  very  outset,  been  urged  against  Dar- 
win's conception  of  very  slow  and  nearly  im- 
perceptible changes,  is  the  enormously  long  time 
required.  If  evolution  does  not  proceed  any 
faster  than  what  we  can  see  at  present,  and  if 
the  process  must  be  assumed  to  have  gone  on 
in  the  same  slow  manner  always,  thousands  of 
millions  of  years  would  have  been  needed  to  de- 
velop the  higher  types  of  animals  and  plants 
from  their  earliest  ancestors. 

Now  it  is  not  at  all  probable  that  the  duration 
of  life  on  earth  includes  such  an  incredibly 
long  time.  Quite  on  the  contrsLYj  the  lifetime 
of  the  earth  seems  to  be  limited  to  a  few 
millions  of  years.  The  researches  of  Lord  Kel- 
vin and  other  eminent  physicists,  seem  to  leave 
no  doubt  on  this  point.  Of  course  all  esti- 
mates of  this  kind  are  only  vague  and  approx- 
imate, but  for  our  present  purposes  they  may 
be  considered  as  sufficiently  exact. 

In  a  paper  published  in  1862  Sir  William 
Thomson  (now  Lord  Kelvin)  first  endeavored  to 
show  that  great  limitation  had  to  be  put  upon 
the  enormous  demand  for  time  made  bv  Lvell, 
Darwin  and  other  biologists.     From  a  consider- 


Periodic  Mutations  711 

ation  of  the  secular  cooling  of  the  earth,  as  de- 
duced from  the  increasing  temperature  in  deep 
mines,  he  concluded  that  the  entire  age  of  the 
earth  must  have  been  more  than  twenty  and  less 
than  forty  millions  of  years,  and  probably  much 
nearer  twenty  than  forty.  His  views  have  been 
much  criticised  by  other  physicists,  but  in  the 
main  they  have  gained  an  ever-increasing  sup- 
port in  the  way  of  evidence.  New  mines  of 
greater  depth  have  been  bored,  and  their  tem- 
peratures have  proved  that  the  figures  of  Lord 
Kelvin  are  strikingly  near  the  truth.  George 
Darwin  has  calculated  that  the  separation  of 
the  moon  from  the  earth  must  have  taken  place 
some  fifty-six  millions  of  years  ago.  Geikie  has 
estimated  the  existence  of  the  solid  crust  of  the 
earth  at  the  most  as  a  hundred  million  years. 
The  first  appearance  of  the  crust  must  soon  have 
been  succeeded  by  the  formation  of  the  seas, 
and  a  long  time  does  not  seem  to  have  been  re- 
quired to  cool  the  seas  to  such  a  degree  that  life 
became  possible.  It  is  very  probable  that  life 
originally  commenced  in  the  great  seas,  and  that 
the  forms  which  are  now  usually  included  in  the 
plankton  or  floating-life  included  the  very  first 
living  beings.  According  to  Brooks,  life  must 
have  existed  in  this  floating  condition  during 
long  primeval  epochs,  and  evolved  nearly  all  the 
main  branches  of  the  animal  and  vegetable  king- 


712  Mutations 

dom  before  sinking  to  the  bottom  of  the  sea,  and 
later  producing  the  vast  number  of  diverse 
forms  which  now  adorn  the  sea  and  land. 

All  these  evolutions,  however,  must  have  been 
very  rapid,  especially  at  the  beginning,  and  to- 
gether cannot  have  taken  more  time  than  the 
figures  given  above. 

The  agency  of  the  larger  streams,  and  the 
deposits  which  they  bring  into  the  seas,  afford 
further  evidence.  The  amount  of  dissolved 
salts,  especially  of  sodium  chloride,  has  been 
made  the  subject  of  a  calculation  by  Joly,  and 
the  amount  of  lime  has  been  estimated  by 
Eugene  Dubois.  Joly  found  fifty-five  and  Du- 
bois thirty-six  millions  of  years  as  the  probable 
duration  of  the  age  of  the  rivers,  and  both  fig- 
ures correspond  to  the  above  dates  as  closely 
as  might  be  expected  from  the  discussion  of  evi- 
dence so  very  incomplete  and  limited. 

All  in  all  it  seems  evident  that  the  duration  of 
life  does  not  comply  with  the  demands  of  the 
conception  of  very  slow  and  continuous  evolu- 
tion. Now  it  is  easily  seen,  that  the  idea  of 
successive  mutations  is  quite  independent  of 
this  difficulty.  Even  assuming  that  some  thou- 
sands of  characters  must  have  been  acquired  in 
order  to  produce  the  higher  animals  and  plants 
of  the  present  time,  no  valid  objection  is  raised. 
The  demands  of  the  biologists  and  the  results  of 


Periodic  Mutations  713 

the  physicists  are  harmonized  on  the  ground  of 
the  theory  of  mutation. 

The  steps  may  be  surmised  to  have  never  been 
essentially  larger  than  in  the  mutations  now 
going  on  under  our  eyes,  and  some  thousands  of 
them  may  be  estimated  as  sufficient  to  account 
for  the  entire  organization  of  the  higher  forms. 
Granting  between  twenty  and  forty  millions 
of  years  since  the  beginning  of  life,  the  intervals 
between  two  successive  mutations  may  have 
been  centuries  and  even  thousands  of  years.  As 
yet  there  has  been  no  objection  cited  against  this 
assumption,  and  hence  we  see  that  the  lack  of 
harmony  between  the  demands  of  biologists  and 
the  results  of  the  physicists  disappears  in  the 
light  of  the  theory  of  mutation. 

Summing  up  the  results  of  this  discussion,  we 
may  justifiably  assert  that  the  conclusions  de- 
rived from  the  observations  and  experiments 
made  with  evening-primroses  and  other  plants 
in  the  main  agree  satisfactorily  with  the  in- 
ferences drawn  from  paleontologic,  geologic 
and  systematic  evidence.  Obviously  these  ex- 
periments are  wonderfully  supported  by  the 
whole  of  our  knowledge  concerning  evolution. 
For  this  reason  the  laws  discovered  in  the  ex- 
perimental garden  may  be  considered  of  great 
importance,  and  they  may  guide  us  in  our  fur- 
ther   inquiries.     Without    doubt   many    minor 


714  Mutations 

points  are  in  need  of  correction  and  elaboration, 
but  such  improvements  of  our  knowledge  will 
gradually  increase  our  means  of  discovering 
new  instances  and  new  proofs. 

The  conception  of  mutation  periods  produc- 
ing swarms  of  species  from  time  to  time,  among 
which  only  a  few  have  a  chance  of  survival, 
promises  to  become  the  basis  for  speculative 
pedigree-diagrams,  as  well  as  for  experimental 
investigations. 


F.    FLUCTUATION 
Lecture  XXV 

GENERAL   LAWS   OF   FLUCTUATION 

The  principle  of  unit-characters  and  of  ele- 
mentary species  leads  at  once  to  the  recognition 
of  two  kinds  of  variability.  The  changes  of 
wider  amplitude  consist  of  the  acquisition  of 
new  units,  or  the  loss  of  already  existing  ones. 
The  lesser  variations  are  due  to  the  degree  of 
activity  of  the  units  themselves. 

Facts  illustrative  of  these  distinctions  were 
almost  wholly  lacking  at  the  time  of  the  first 
publication  of  Darwin's  theories.  It  was  a  bold 
conception  to  point  out  the  necessity  for  such 
distinction  on  purely  theoretical  grounds.  Of 
course  some  sports  were  well  known  and  fluc- 
tuations were  evident,  but  no  exact  analysis  of 
the  details  was  possible,  a  fact  that  was  of  great 
importance  in  the  demonstration  of  the  theory 
of  descent.  The  lack  of  more  definite  knowl- 
edge upon  this  matter  was  keenly  felt  by  Dar- 

715 


716  Fluctuations 

win,  and  exercised  much  influence  upon  his 
views  at  various  times. 

Quetelet's  famous  discovery  of  the  law  of 
fluctuating  variability  changed  the  entire  situa- 
tion and  cleared  up  many  difficulties.  While  a 
clear  conception  of  fluctuations  was  thus  gained, 
mutations  were  excluded  from  consideration, 
being  considered  as  very  rare,  or  non-existent. 
They  seemed  wholly  superfluous  for  the  theory 
of  descent,  and  very  little  importance  was  at- 
tached to  their  study.  Current  scientific  belief 
in  the  matter  has  changed  only  in  recent 
years.  Mendel's  law  of  varietal  hybrids  is 
based  upon  the  principle  of  unit-characters,  and 
the  validity  of  this  conception  has  thus  been 
brought  home  to  many  investigators. 

A  study  of  fluctuating  or  individual  variabil- 
ity, as  it  was  formerly  called,  is  now  carried  on 
chiefly  by  mathematical  methods.  It  is  not  my 
purpose  to  go  into  details,  as  it  would  re- 
quire a  separate  course  of  lectures.  I  shall  con- 
sider the  limits  between  fluctuation  and  muta- 
tion only,  and  attempt  to  set  forth  an  adequate 
idea  of  the  principles  of  the  first  as  far  as  they 
touch  these  limits.  The  mathematical  treat- 
ment of  the  facts  is  no  doubt  of  very  great  value, 
but  the  violent  discussions  now  going  on  be- 
tween mathematicians  such  as  Pearson,  Kap- 
teyn  and  others  should  warn  biologists  to  ab- 


Laws  of  Fluctuations  111 

stain  from  the  use  of  methods  which  are  not 
necessary  for  the  furtherance  of  experimental 
work. 

Fortunately,  Quetelet's  law  is  a  very  clear 
and  simple  one,  and  quite  sufficient  for  our  con- 
siderations. It  claims  that  for  biologic  phe- 
nomena the  deviations  from  the  average  comply 
with  the  same  laws  as  the  deviations  from  the 
average  in  any  other  case,  if  ruled  by  chance 
only.  The  meaning  of  this  assertion  will  be- 
come clear  by  a  further  discussion  of  the  facts. 

First  of- all,  fluctuating  variability  is  an  al- 
most universal  phenomenon.  Every  organ  and 
every  quality  may  exhibit  it.  Some  are  very 
variable,  while  others  seem  quite  constant. 
Shape  and  size  vary  almost  indefinitely,  and  the 
chemical  composition  is  subject  to  the  same  law, 
as  is  well  known  for  the  amount  of  sugar  in 
sugar-beets.  Numbers  are  of  course  less  liable 
to  changes,  but  the  numbers  of  the  rays  of  um- 
bels, or  ray-florets  in  the  composites,  of  pairs  of 
blades  in  pinnate  leaves,  and  even  of  stamens 
and  carpels  are  known  to  be  often  exceedingly 
variable.  The  smaller  numbers  however,  are 
more  constant,  and  deviations  from  the  quinate 
structure  of  flowers  are  rare.  Complicated 
structures  are  generally  capable  of  only  slight 
deviations. 

From  a  broad  point  of  view,  fluctuating  varia- 


718  Fluctuations 

bility  falls  under  two  heads.  They  obey  quite 
the  same  laws  and  are  therefore  easily  confused, 
but  with  respect  to  questions  of  heredity  they 
should  be  carefully  separated.  They  are  des- 
ignated by  the  terms  individual  and  partial 
fluctuation.  Individual  variability  indicates 
the  differences  between  individuals,  while 
partial  variability  is  limited  to  the  devia- 
tions shown  by  the  parts  of  one  organ- 
ism from  the  average  structure.  The  same 
qualities  in  some  cases  vary  individually  and  in 
others  partially.  Even  stature,  which  is  as 
markedly  individual  for  annual  and  biennial 
plants  as  it  is  for  man,  becomes  partially  variant 
in  the  case  of  perennial  herbs  with  numbers  of 
stems.  Often  a  character  is  only  developed  once 
in  the  whole  course  of  evolution,  as  for  instance, 
the  degree  of  connation  of  the  seed-leaves  in 
tricotyls  and  in  numerous  cases  it  is  impos- 
sible to  tell  whether  a  character  is  individual  or 
partial.  Consequently  such  minute  details 
are  generally  considered  to  have  no  real  im- 
portance for  the  hereditary  transmission  of  the 
character  under  discussion. 

Fluctuations  are  observed  to  take  place  only 
in  two  directions.  The  quality  may  increase  or 
decrease,  but  is  not  seen  to  vary  in  any  other 
way.  This  rule  is  now  widely  established  by 
numerous  investigations,  and  is  fundamental  to 


Laivs  of  Fluctuatioyis  719 

the  whole  method  of  statistical  investigation. 
It  is  equally  important  for  the  discussion  of  the 
contrast  between  fluctuations  and  mutations, 
and  for  the  appreciation  of  their  part  in  the 
general  progress  of  organization.  Mutations 
are  going  on  in  all  directions,  producing,  if  they 
are  progressive,  something  quite  new  every 
time.  Fluctuations  are  limited  to  increase  and 
decrease  of  what  is  already  available.  They 
may  produce  plants  with  higher  stems,  more 
petals  in  the  flowers,  larger  and  more  palatable 
fruits,  but  obviously  the  first  petal  and  the  first 
berry  cannot  have  originated  by  the  simple  in- 
crease of  some  older  quality.  Intermediates 
may  be  found,  and  they  may  mark  the  limit,  but 
the  demonstration  of  the  absence  of  a  limit  is 
quite  another  question.  It  would  require  the 
two  extremes  to  be  shown  to  belong  to  one  unit, 
complying  with  the  simple  law  of  Quetelet. 

Nourishment  is  the  potent  factor  of  fluctuat- 
ing variability.  Of  course  in  thousands  of  cases 
our  knowledge  is  not  sufficient  to  allow  us  to  ana- 
lyze this  relation,  and  a  number  of  phases  of  the 
phenomenon  have  been  discovered  only  quite 
recently.  But  the  fact  itself  is  thoroughly  mani- 
fest, and  its  appreciation  is  as  old  as  horticul- 
tural science.  Knight,  who  lived  at  the  begin- 
ning of  the  last  century,  has  laid  great  stress 
upon  it,  and  it  has  since  influenced  practice  in  a 


720  Fluctuations 

large  measure.  Moreover,  Knight  pointed  out 
more  than  once  that  it  is  the  amount  of  nourish- 
ment, not  the  quality  of  the  various  factors,  that 
exercises  the  determinative  influence.  Nourish- 
ment is  to  be  taken  in  the  widest  sense  of  the 
word,  including  all  favorable  and  injurious  ele- 
ments. Light  and  temperature,  soil  and  space, 
water  and  salts  are  equally  active,  and  it  is  the 
harmonious  cooperation  of  them  all  that  rules 
growth. 

We  treated  this  important  question  at  some 
length,  when  dealing  with  the  anomalies  of  the 
opium-poppies,  consisting  of  the  conversion  of 
stamens  into  supernumerary  pistils.  The  de- 
pendency upon  external  influences  which  this 
change  exhibited  is  quite  the  same  as  that  shown 
by  fluctuating  variability  at  large.  We  inquired 
into  the  influence  of  good  and  bad  soil,  of  sun- 
light and  moisture  and  of  other  concurrent  fac- 
tors. Especial  emphasis  was  laid  upon  the 
great  differences  to  which  the  various  individ- 
uals of  the  same  lot  may  be  exposed,  if  moisture 
and  manure  differ  on  different  portions  of  the 
same  bed  in  a  way  unavoidable  even  by  the  most 
careful  preparation.  Some  seeds  germinate  on 
moist  and  rich  spots,  while  their  neighbors  are 
impeded  by  local  dryness,  or  by  distance  from 
manure.  Some  come  to  light  on  a  sunny  day, 
and  increase  their  first  leaves  rapidly,  while  on 


Laws  of  Fluctuations  721 

the  following  day  the  weather  may  be  unfavor- 
able and  greatly  retard  growth.  The  individual 
differences  seem  to  be  due,  at  least  in  a  very 
great  measure,  to  such  apparent  trifles. 

On  the  other  hand  partial  differences  are 
often  manifestly  due  to  similar  causes.  Con- 
sidering the  various  stems  of  plants,  which  mul- 
tiply themselves  by  runners  or  by  buds  on  the 
roots,  the  assertion  is  in  no  need  of  further 
proof.  The  same  holds  good  for  all  cases  of 
artificial  multiplication  by  cuttings,  or  by  other 
vegetative  methods.  But  even  if  we  limit  our- 
selves to  the  leaves  of  a  single  tree,  or  the 
branches  of  a  shrub,  or  the  flowers  on  a  plant, 
the  same  rule  prevails.  The  development  of 
the  leaves  is  dependent  on  their  position,  wheth- 
er inserted  on  strong  or  weak  branches,  exposed 
to  more  or  less  light,  or  nourished  by  strong  or 
weak  roots.  The  vigor  of  the  axillary  buds 
and  of  the  branches  which  they  may  produce  is 
dependent  upon  the  growth  and  activity  of  the 
leaves  to  which  the  buds  are  axillary. 

This  dependency  on  local  nutrition  leads  to 
the  general  law  of  periodicity,  which,  broadly 
speaking,  governs  the  occurrence  of  the  fluctuat- 
ing deviations  of  the  organs.  This  law  of  pe- 
riodicity involves  the  general  principle  that 
every  axis,  as  a  rule,  increases  in  strength  when 


722  Fluctuations 

growing,  but  sooner  or  later  reaches  a  maximum 
and  may  afterwards  decrease. 

This  periodic  augmentation  and  declination  is 
often  boldly  manifest,  though  in  other  cases  it 
may  be  hidden  by  the  effect  of  alternate  influ- 
ences. Pinnate  leaves  generally  have  their 
lower  blades  smaller  than  the  upper  ones,  the 
longest  being  seen  sometimes  near  the  apex 
and  sometimes  at  a  distance  from  it.  Branches 
bearing  their  leaves  in  two  rows  often  afford 
quite  as  obvious  examples,  and  shoots  in  gen- 
eral comply  with  the  same  rule.  Germinating 
plants  are  very  easy  of  observation  on  this 
point.  When  they  are  very  weak  they  produce 
only  small  leaves.  But  their  strength  gradually 
increases  and  the  subsequent  organs  reach 
fuller  dimensions  until  the  maximum  is  at- 
tained. The  phenomenon  is  so  common  that  its 
importance  is  usually  overlooked.  It  should  be 
considered  as  only  one  instance  of  a  rule,  which 
holds  good  for  all  stems  and  all  branches,  and 
which  is  everywhere  dependent  on  the  relation 
of  growth  to  nutrition. 

The  rule  of  periodicity  not  only  affects  the 
size  of  the  organs,  but  also  their  number,  when- 
ever these  are  largely  variable.  Umbellate 
plants  have  numerous  rays  on  the  umbels  of 
strong  stems,  but  the  number  is  seen  to  decrease 
and  to  become  very  small  on  the  weakest  lateral 


Laivs  of  Fluctuations  723 

branches.  The  same  holds  good  for  the  number 
of  ray-florets  in  the  flower-heads  of  the  com- 
posites, even  for  the  nmnber  of  stigmas  on  the 
ovaries  of  the  poppies,  which  on  weak  branches 
may  be  reduced  to  as  few  as  three  or  four. 
Many  other  instances  could  be  given. 

One  of  the  best  authenticated  cases  is  the  de- 
pendency of  partial  fluctuation  on  the  season 
and  on  the  weather.  Flowers  decline  when  the 
season  comes  to  an  end,  become  smaller  and  less 
brightly  colored.  The  number  of  ray-florets  in 
the  flower-heads  is  seen  to  decrease  towards  the 
fall.  Extremes  become  rarer,  and  often  the 
deviations  from  the  average  seem  nearly  to  dis- 
appear. Double  flowers  comply  with  this  rule 
very  closely,  and  many  other  cases  will  easily 
occur  to  any  student  of  nature. 

Of  course,  the  relation  to  nourishment  is  dif- 
ferent for  individual  and  partial  fluctuations. 
Concerning  the  first,  the  period  of  development 
of  the  germ  within  the  seed  is  decisive.  Even 
the  sexual  cells  may  be  in  widely  different  condi- 
tions at  the  moment  of  fusion,  and  perhaps  this 
state  of  the  sexual  cells  includes  the  whole  mat- 
ter of  the  decision  for  the  average  characters  of 
the  new  individual.  Partial  fluctuation  com- 
mences as  soon  as  the  leaves  and  buds  begin  to 
form,  and  all  later  changes  in  nutrition  can 
only    cause    partial    differences.     All    leaves, 


724  Fluctuations 

buds,  branches,  and  flowers  must  come  under 
the  influence  of  external  conditions  during  the 
juvenile  period,  and  so  are  liable  to  attain  a  de- 
velopment determined  in  part  by  the  action  of 
these  factors. 

Before  leaving  these  general  considerations, 
we  must  direct  our  attention  to  the  question  of 
utility.  Obviously,  fluctuating  variability  is 
a  very  useful  contrivance,  in  many  cases  at 
least.  It  appears  all  the  more  so,  as  its  relation 
to  nutrition  becomes  manifest.  Here  two  as- 
pects are  intimately  combined.  More  nutrient 
matter  produces  larger  leaves  and  these  are  in 
their  turn  more  fit  to  profit  by  the  abundance  of 
nourishment.  So  it  is  with  the  number  of 
flowers  and  flower-groups,  and  even  with  the 
numbers  of  their  constituent  organs.  Better 
nourishment  produces  more  of  them,  and  there- 
by makes  the  plant  adequate  to  make  a 
fuller  use  of  the  available  nutrient  substances. 
Without  fluctuation  such  an  adjustment  would 
hardly  be  possible,  and  from  all  our  notions  of 
usefulness  in  nature,  we  therefore  must  recog- 
nize the  efficiency  of  this  form  of  variability. 

In  other  respects  the  fluctuations  often  strike 
us  as  quite  useless  or  even  as  injurious.  The 
numbers  of  stamens,  or  of  carpels  are  dependent 
on  nutrition,  but  their  fluctuation  is  not  known 
to  have  any  attraction  for  the  visiting  insects. 


Laws  of  Fluctuations  725 

If  the  deviations  become  greater,  they  might 
even  become  detrimental.  The  flowers  of  the 
St.  Johnswort,  or  Hypericum  perforatum, 
usually  have  five  petals,  but  the  number  varies 
from  three  to  eight  or  more.  Bees  could  hardly 
be  misled  by  such  deviations.  The  carpels  of 
buttercups  and  columbines,  the  cells  in  the  cap- 
sules of  cotton  and  many  other  plants  are  vari- 
able in  number.  The  number  of  seeds  is  there- 
by regulated  in  accordance  with  the  available 
nourishment,  but  whether  any  other  useful  pur- 
pose is  served,  remains  an  open  question.  Vari- 
ations in  the  honey-guides  or  in  the  pattern  of 
color-designs  might  easily  become  injurious  by 
deceiving  insects,  and  such  instances  as  the 
great  variability  of  the  spots  on  the  corolla  of 
some  cultivated  species  of  monkey-flowers,  for 
instance,  the  Mimulus  quinquevulnerus,  could 
hardly  be  expected  to  occur  in  wild  plants.  For 
here  the  dark  brown  spots  vary  between  nearly 
complete  deficiency  up  to  such  predominancy  as 
almost  to  hide  the  pale  yellow  ground-color. 

After  this  hasty  survey  of  the  causes  of  fluc- 
tuating variability,  we  now  come  to  a  discussion 
of  Quetelet's  law.  It  asserts  that  the  deviations 
from  the  average  obey  the  law  of  probability. 
They  behave  as  if  they  were  dependent  on 
chance  only. 

Everyone  knows  that  the  law  of  Quetelet  can 


726  Fluctuations 

be  demonstrated  the  most  readily  by  placing  a 
sufficient  nmnber  of  adult  men  in  a  row,  arrange 
ing  them  according  to  their  size.  The  line  pass- 
ing over  their  heads  proves  to  be  identical  with 
that  given  by  the  law  of  probability.  Quite 
in  the  same  way,  stems  and  branches,  leaves  and 
petals  and  even  fruits  can  be  arranged,  and 
they  will  in  the  main  exhibit  the  same  line  of 
variability.  Such  groups  are  very  striking,  and 
at  the  first  glance  show  that  the  large  majority 
of  the  specimens  deviate  from  the  mean  only  to 
a  very  small  extent.  Wider  deviations  are  far 
more  rare,  and  their  number  lessens,  the  greater 
the  deviation,  as  is  shown  by  the  curvature 
of  the  line.  It  is  almost  straight  and  horizontal 
in  the  middle  portion,  while  at  the  ends  it 
rapidly  declines,  going  sharply  downward  at 
one  extreme  and  upward  at  the  other. 

It  is  obvious  however,  that  in  these  groups 
the  leaves  and  other  organs  could  conveniently 
be  replaced  by  simple  lines,  indicating  their  size. 
The  result  would  be  quite  the  same,  and  the  lines 
could  be  placed  at  arbitrary,  but  equal  dis- 
tances. Or  the  sizes  could  be  expressed  by  fig- 
ures, the  compliance  of  which  with  the  general 
law  could  be  demonstrated  by  simple  methods 
of  calculation.  In  this  manner  the  variability 
of  different  organs  can  easily  be  compared. 

Another  method  of  demonstration  consists  in 


Laws  of  Fluctuations  727 

grouping  the  deviations  into  previously  fixed 
divisions.  For  this  purpose  the  variations 
are  measured  by  standard  units,  and  all  the  in- 
stances that  fall  between  two  limits  are  consid- 
ered to  constitute  one  group.  Seeds  and  small 
fruits,  berries  and  many  other  organs  may 
conveniently  be  dealt  with  in  this  way.  As  an 
example  we  take  ordinary  beans  and  select  them 
according  to  their  size.  This  can  be  done  in 
different  ways.  On  a  small  piece  of  board  a 
long  wedge-shaped  slit  is  made,  into  which  seeds 
are  pushed  as  far  as  possible.  The  margin  of 
the  wedge  is  calibrated  in  such  a  manner  that  the 
figures  indicate  the  width  of  the  wedge  at  the 
corresponding  place.  By  this  device  the  figure 
up  to  which  a  bean  is  pushed  at  once  shows  its 
length.  Fractions  of  millimeters  are  neglected, 
and  the  beans,  after  having  been  measured,  are 
thrown  into  cylindrical  glasses  of  the  same 
width,  each  glass  receiving  only  beans  of  equal 
length.  It  is  clear  that  by  this  method  the 
height  to  which  beans  fill  the  glasses  is  ap- 
proximately a  measure  of  their  number.  If  now 
the  glasses  are  put  in  a  row  in  the  proper  se- 
quence, they  at  once  exhibit  the  shape  of  a  line 
which  corresponds  to  the  law  of  chance.  In  this 
case  however,  the  line  is  drawn  in  a  different 
manner  from  the  first.  It  is  to  be  pointed  out 
that  the  glasses  may  be  replaced  by  lines  in- 


728  Fluctuations 

dicating  the  height  of  their  contents,  and  that, 
in  order  to  reach  a  more  easy  and  correct  state- 
ment, the  length  of  the  lines  may  simply  be  made 
proportionate  to  the  number  of  the  beans  in 
each  glass.  If  such  lines  are  erected  on  a  com- 
mon base  and  at  equal  distances,  the  line  which 
unites  their  upper  ends  will  be  the  expression  of 
the  fluctuating  variability  of  the  character  under 
discussion. 

The  same  inquiry  may  be  made  with  other 
seeds,  with  fruits,  or  other  organs.  It  is  quite 
superfluous  to  arrange  the  objects  themselves, 
and  it  is  sufficient  to  arrange  the  figures  in- 
dicating their  value.  In  order  to  do  this  a 
basal  line  is  divided  into  equal  parts,  the  de- 
marcations corresponding  to  the  standard-units 
chosen  for  the  test.  The  observed  values  are 
then  written  above  this  line,  each  finding  its 
place  between  the  two  demarcations,  which  in- 
clude its  value.  It  is  very  interesting  and 
stimulating  to  construct  such  a  group.  The 
first  figures  may  fall  here  and  there,  but  very 
soon  the  vertical  rows  on  the  middle  part  of 
the  basal  line  begin  to  increase.  Sometimes 
ten  or  twenty  measurements  will  suffice  to  make 
the  line  of  chance  appear,  but  often  indentations 
will  remain.  With  the  increasing  number  of 
the   observations   the   irregularities   gradually 


Laws  of  Fluctuations  729 

disappear,  and  the  line  becomes  smoother  and 
more  uniformly  curved. 

This  method  of  arranging  the  figures  directly 
on  a  basal  line  is  very  convenient,  whenever  ob- 
servations are  made  in  the  field  or  garden. 
Very  few  instances  need  be  recorded  to  obtain 
an  appreciation  of  the  mean  value,  and  to  show 
what  may  be  expected  from  a  continuance  of 
the  test.  The  method  is  so  simple  and  so 
striking,  and  so  wholly  independent  of  any 
mathematical  development  that  it  should  be  ap- 
plied in  all  cases  in  which  it  is  desired  to  ascer- 
tain the  average  value  of  any  organ,  and  the 
measure  of  the  attendant  deviations. 

I  cite  an  instance,  secured  by  counting  the 
ray-florets  on  the  flower-heads  of  the  corn-mari- 
gold or  Chrysanthemum  segetum.  It  was  that, 
by  which  I  was  enabled  to  select  the  plant,  which 
afterwards  showed  the  first  signs  of  a  double 
head.     I  noted  them  in  this  way : 

47 

47  52 

41  54  68 

44  50  62  75 

36  45  58  65  72  —  99 

Of  course  the  figures  might  be  replaced  in 
this  work  by  equidistant  dots  or  by  lines,  but 
experience  teaches  that  the  chance  of  making 
mistakes  is  noticeably  lessened  by  writing  down 


730  Fluctuations 

the  figures  themselves.  Whenever  decimals  are 
made  use  of  it  is  obviously  the  best  plan  to  keep 
the  figures  themselves.  For  afterwards  it  often 
becomes  necessary  to  arrange  them  according 
to  a  somewhat  different  standard. 

Uniting  the  heads  of  the  vertical  rows  of  fig- 
ures by  a  line,  the  form  corresponding  to  Que- 
telet's  law  is  easily  seen.  In  the  main  it  is 
always  the  same  as  the  line  shown  by  the  meas- 
urements of  beans  and  seeds.  It  proves  a  dense 
crowding  of  the  single  instances  around  the 
average,  and  on  both  sides  of  the  mass  of  the 
observations,  a  few  wide  deviations.  These  be- 
come more  rare  in  proportion  to  the  amount  of 
their  divergency.  On  both  sides  of  the  average 
the  line  begins  by  falling  very  rapidly,  but  then 
bends  slowly  so  as  to  assume  a  nearly  horizon- 
tal direction.  It  reaches  the  basal  line  only  be- 
yond the  extreme  instances. 

It  is  quite  evident  that  all  qualities,  which 
can  be  expressed  by  figures,  may  be  treated  in 
this  way.  First  of  all  the  organs  occurring  in 
varying  numbers,  as  for  instance  the  ray-florets 
of  composites,  the  rays  of  umbels,  the  blades  of 
pinnate  and  palmate  leaves,  the  numbers  of 
veins,  etc.,  are  easily  shown  to  comply  with 
the  same  general  rule.  Likewise  the  amount 
of  chemical  substances  can  be  expressed 
in  percentage  numbers,  as  is  done  on  a  large 


Laws  of  Fluctuations  731 

scale  with  sugar  in  beets  and  sugar-cane,  with 
starch  in  potatoes  and  in  other  instances. 
These  figures  are  also  found  to  follow  the  same 
law. 

All  qualities  which  are  seen  to  increase  and 
to  decrease  may  be  dealt  with  in  the  same  man- 
ner, if  a  standard  unit  for  their  measure- 
ment can  be  fixed.  Even  the  colors  of  flowers 
may  not  escape  our  inquiry. 

If  we  now  compare  the  lines,  compiled  from 
the  most  divergent  cases,  they  will  be  found  to 
exhibit  the  same  features  in  the  main.  Ordi- 
narily the  curve  is  symmetrical,  the  line  sloping 
down  on  botli  sides  after  the  same  manner.  But 
it  is  not  at  all  rare  that  the  inclination  is 
steep  on  one  side  and  gradual  on  the  other.  This 
is  noticeably  the  case  if  the  observations  relate 
to  numbers,  the  average  of  which  is  near  zero. 
Here  of  course  the  allowance  for  variation  is  on- 
ly small  on  one  side,  while  it  may  increase  with- 
out distinct  limits  on  the  alternate  slope.  So  it 
is  for  instance  with  the  numbers  of  ray-florets 
in  the  example  given  on  p.  729.  Such  divergent 
cases,  however,  are  to  be  considered  as  excep- 
tions to  the  rule,  due  to  some  unknown  cause. 

Heretofore  we  have  discussed  the  empirical 
side  of  the  problem  only.  For  the  purpose 
of  experimental  study  of  questions  of  hered- 
ity this  is  ordinarily  quite  sufficient.     The  in- 


732  Fluctuations 

quiry  into  the  phenomenon  of  regression,  or  of 
the  relation  of  the  degree  of  deviation  of  the 
progeny  to  that  of  their  parents,  and  the  selec- 
tion of  extreme  instances  for  multiplication  are 
obviously  independent  of  mathematical  consid- 
erations. On  the  other  hand  an  important  in- 
quiry lies  in  the  statistical  treatment  of  these 
phenomena,  and  such  treatment  requires  the 
use  of  mathematical  methods. 

Statistics  however,  are  not  included  in  the 
object  of  these  lectures,  and  therefore  I  shall 
refrain  from  an  explanation  of  the  method  of 
their  preparation  and  limit  myself  to  a  general 
comparison  of  the  observed  lines  with  the  law 
of  chance.  Before  going  into  the  details,  it 
should  be  repeated  once  more  that  the  empirical 
result  is  quite  the  same  for  individual  and  for 
partial  fluctuations.  As  a  rule,  the  latter  occur 
in  far  greater  number,  and  are  thus  more  easily 
investigated,  but  individual  or  personal  aver- 
ages have  also  been  studied. 

Newton  discovered  that  the  law  of  chance  can 
be  expressed  by  very  simple  mathematical  cal- 
culations. Without  going  into  details,  we  may 
at  once  state  that  these  calculations  are  based 
upon  his  binomium.  If  the  fonn  (a  +  b)°  is  cal- 
culated for  some  value  of  the  exponent,  and  if 
the  values  of  the  coefficients  after  develop- 
ment are  alone  considered,  they  yield  the  basis 


Laivs  of  Fluctuations  733 

for  the  construction  of  what  is  called  the  line  or 
curve  of  probability.  For  this  construction  the 
coefficients  are  used  as  ordinates,  the  length  of 
which  is  to  be  made  proportionate  to  their  value. 
If  this  is  done,  and  the  ordinates  are  arranged 
at  equal  distances,  the  line  which  unites  their 
summits  is  the  desired  curve.  At  first  glance  it 
exhibits  a  form  quite  analogous  to  the  curves 
of  fluctuating  variability,  obtained  by  the  meas- 
urements of  beans  and  in  other  instances.  Both 
lines  are  symmetrical  and  slope  rapidly  down  in 
the  region  of  the  average,  while  with  increasing 
distance  they  gradually  lose  their  steep  incli- 
nation, becoming  nearly  parallel  to  the  base  at 
their  termination. 

This  similarity  between  such  empirical  and 
theoretical  lines  is  in  itself  an  empirical  fact. 
The  causes  of  chance  are  assumed  to  be  innu- 
merable, and  the  whole  calculation  is  based  on 
this  assumption.  The  causes  of  the  fluctuations 
of  biological  phenomena  have  not  as  yet  been 
critically  examined  to  such  an  extent  as  to  allow 
of  definite  conceptions.  The  term  nourishment 
manifestly  includes  quite  a  number  of  separate 
factors,  as  light,  space,  temperature,  moisture, 
the  physical  and  chemical  conditions  of  the  soil 
and  the  changes  of  the  weather.  Without  doubt 
the  single  factors  are  very  numerous,  but 
whether  thev  are  numerous  enough  to  be  treated 


734  Fluctuations 

as  innumerable,  and  thereby  to  explain  the  laws 
of  fluctuations,  remains  uncertain.  Of  course 
the  easiest  way  is  to  assume  that  they  combine 
in  the  same  manner  as  the  causes  of  chance,  and 
that  this  is  the  ground  of  the  similarity  of  the 
curves.  On  the  other  hand,  it  is  manifestly  of 
the  highest  importance  to  inquire  into  the  part 
the  several  factors  play  in  the  determination 
of  the  curves.  It  is  not  at  all  improbable  that 
some  of  them  have  a  larger  influence  on  indi- 
vidual, and  others  on  partial,  fluctuations.  If 
this  were  the  case,  their  importance  with  respect 
to  questions  of  heredity  might  be  widely  differ- 
ent. In  the  present  state  of  our  knowledge  the 
fluctuation-curves  do  not  contribute  in  any 
large  measure  to  an  elucidation  of  the  causes. 
Where  these  are  obvious,  they  are  so  without 
statistics,  exactly  as  they  were,  previous  to 
Quetelet's  discovery. 

In  behalf  of  a  large  number  of  questions  con- 
cerning heredity  and  selection,  it  is  very  desir- 
able to  have  a  somewhat  closer  knowledge  of 
these  curves.  Therefore  I  shall  try  to  point  out 
their  more  essential  features,  as  far  as  this  can 
be  done  without  mathematical  calculations. 

At  a  first  glance  three  points  strike  us,  the 
average  or  the  summit  of  the  cur\^e,  and  the  ex- 
tremes. If  the  general  shape  is  once  denoted  by 
the  results   of   observations   or  by  the   coeffi- 


Laws  of  Fluctuations  735 

cients  of  the  binomium,  all  further  details  seem 
to  depend  upon  them.  In  respect  to  the  average 
this  is  no  doubt  the  case ;  it  is  an  empirical  value 
without  need  of  any  further  discussion.  The 
more  the  number  of  the  observations  increases, 
the  more  assured  and  the  more  correct  is  this 
mean  value,  but  generally  it  is  the  same  for 
smaller  and  for  larger  groups  of  observations. 

This  however,  is  not  the  case  with  the  ex- 
tremes. It  is  quite  evident  that  small  groups 
have  a  chance  of  containing  neither  of  them. 
The  more  the  number  of  the  observations  in- 
creases, the  larger  is  the  chance  of  extremes.  As 
a  rule,  and  excluding  exceptional  cases,  the  ex- 
treme deviations  will  increase  in  proportion  to 
the  number  of  cases  examined.  In  a  hundred 
thousand  beans  the  smallest  one  and  the  largest 
one  may  be  expected  to  differ  more  widely  from 
one  another  than  in  a  few  hundred  beans  of  the 
same  sample.  Hence  the  conclusion  that  ex- 
tremes are  not  a  safe  criterion  for  the  discus- 
sion of  the  curves,  and  not  at  all  adequate  for 
calculations,  which  must  be  based  upon  more 
definite  values. 

A  real  standard  is  afforded  by  the  steepness 
of  the  slope.  This  may  be  unequal  on  the  two 
sides  of  one  curve,  and  likewise  it  may  differ  for 
different  cases.  This  steepness  is  usually  meas- 
ured by  means  of  a  point  on  the  half  cur\^e  and 


736  Fluctuations 

for  this  purpose  a  point  is  chosen  which  lies 
exactly  half  way  between  the  average  and  the 
extreme.  Not  however  half  way  with  respect  to 
the  amplitude  of  the  extreme  deviation,  for  on 
this  ground  it  would  partake  of  the  uncertainty 
of  the  extreme  itself.  It  is  the  point  on  the 
curve  which  is  surpassed  by  half  the  number, 
and  not  reached  by  the  other  half  of  the  num- 
ber of  the  observations  included  in  the  half  of 
the  curve.  This  point  corresponds  to  the  im- 
portant value  called  the  probable  error,  and 
was  designated  by  Galton  as  the  quartile.  For 
it  is  evident  that  the  average  and  the  two  quar- 
tiles  divide  the  whole  of  the  observations  into 
four  equal  parts. 

Choosing  the  quartiles  as  the  basis  for  cal- 
culations we  are  independent  of  all  the  second- 
ary causes  of  error,  which  necessarily  are  in- 
herent in  the  extremes.  At  a  casual  examina- 
tion, or  for  demonstrative  purposes,  the  ex- 
tremes may  be  prominent,  but  for  all  further 
considerations  the  quartiles  are  the  real  values 
upon  which  to  rest  calculations. 

Moreover  if.  the  agreement  with  the  law  of 
probability  is  once  conceded,  the  whole  curve  is 
defined  by  the  average  and  the  quartiles,  and 
the  result  of  hundreds  of  measurements  or 
countings  may  be  summed  up  in  three,  or,  in 


Laws  of  Fluctuations  1^1 

the  case  of  symmetrical  curves,  perhaps  in  two 
figures. 

Also  in  comparing  different  curves  with  one 
another,  the  quartiles  are  of  great  importance. 
Whenever  an  empirical  fluctuation-curve  is  to  be 
compared  with  the  theoretical  form,  or  when 
two  or  more  cases  of  variability  are  to  be  con- 
sidered under  one  head,  the  lines  are  to  be 
drawn  on  the  same  base.  It  is  manifest  that 
the  averages  must  be  brought  upon  the  same 
ordinate,  but  as  to  the  steepness  of  the  line, 
much  depends  on  the  manner  of  plotting.  Here 
we  must  remember  that  the  mutual  distance  of 
the  ordinates  has  been  a  wholly  arbitrary 
one  in  all  our  previous  considerations.  And 
so  it  is,  as  long  as  only  one  curve  is  considered 
at  a  time.  But  as  soon  as  two  are  to  be  com- 
pared, it  is  obvious  that  free  choice  is  no  longer 
allowed.  The  comparison  must  be  made 
on  a  common  basis,  and  to  this  effect  the  quar- 
tiles must  be  brought  together.  They  are  to  lie 
on  the  same  ordinates.  If  this  is  done,  each 
division  of  the  base  corresponds  to  the  same 
proportionate  number  of  individuals,  and  a 
complete  comparison  is  made  possible. 

On  the  ground  of  such  a  comparison  we  may 
thus  assert  that  fluctuations,  however  different 
the  organs  or  qualities  observed,  are  the  same 
whenever  their  curves  are  seen  to  overlap  one 


738  Fluctuations 

another.  Furthermore,  whenever  an  empirical 
curve  agrees  in  this  manner  with  the  theoretical 
one,  the  fluctuation  complies  with  Quetelet's  law, 
and  may  be  ascribed  to  quite  ordinary  and  uni- 
versal causes.  But  if  it  seems  to  diverge  from 
this  line,  the  cause  of  this  divergence  should  be 
inquired  into. 

Such  abnormal  curves  occur  from  time  to 
time,  but  are  rare.  Unsymmetrical  instances 
have  already  been  alluded  to,  and  seem  to  be 
quite  frequent.  Another  deviation  from  the 
rule  is  the  presence  of  more  than  one  summit. 
This  case  falls  under  two  headings.  If  the  ray- 
florets  of  a  composite  are  counted,  and  the  fig- 
ures brought  into  a  curve,  a  prominent  summit 
usually  corresponds  to  the  average.  But  next 
to  this,  and  on  both  sides,  smaller  summits  are 
to  be  seen.  On  a  close  inspection  these  summits 
are  observed  to  fall  on  the  same  ordinates,  on 
which,  in  the  case  of  allied  species,  the  main 
apex  lies.  The  specific  character  of  one  form 
is  thus  repeated  as  a  secondary  character  on  an 
allied  species.  Ludwig  discovered  that  these 
secondary  summits  comply  with  the  rule  discov- 
ered by  Braun  and  Schimper,  stating  the  rela- 
tion of  the  subsequent  figures  of  the  series. 
This  series  gives  the  terms  of  the  dis- 
position of  leaves  in  general,  and  of  tlie 
bracts   and  flowers   on  the  composite  flower- 


Laws  of  Fluctuations  739 

heads  in  our  particular  case.  It  is  the 
series  to  which  we  have  already  alluded 
when  dealing  with  the  arrangement  of  the  leaves 
on  the  twisted  teasels.  It  commences  with 
1  and  2  and  each  following  figure  is  equal  to 
the  sum  of  its  two  precedents.  The  most  com- 
mon figures  are  3,  5,  8,  13,  18,  21,  higher  cases 
seldom  coming  under  observation.  Now  the 
secondary  summits  of  the  ray-curves  of  the 
composites  are  seen  to  agree,  as  a  rule,  with 
these  figures.  Other  instances  could  readily  be 
given. 

Our  second  heading  includes  those  cases 
which  exhibit  two  summits  of  equal  or  nearly 
equal  height.  Such  cases  occur  when  dif- 
ferent races  are  mixed,  each  retaining  its  own 
average  and  its  own  curve-summit.  We  have  al- 
ready demonstrated  such  a  case  when  dealing 
with  the  origin  of  our  double  corn-chrysanthe- 
mum. The  wild  species  culminates  with  13  rays, 
and  the  grandiflorum  variety  with  21.  Often 
the  latter  is  found  to  be  impure,  being  mixed 
with  the  typical  species  to  a  varying  extent. 
This  is  not  easily  ascertained  by  a  casual  in- 
spection of  the  cultures,  but  the  true  condition 
will  promptly  betray  itself,  if  curves  are  con- 
structed. In  this  way  curves  may  in  many  in- 
stances be  made  use  of  to  discover  mixed  races. 

Double  curves  may  also  result  from  the  inves- 


740  Fluctuations 

tigation  of  true  double  races,  or  ever-sporting 
varieties.  The  striped  snapdragon  shows  a 
curve  of  its  stripes  with  two  summits,  one  cor- 
responding to  the  average  striped  flowers,  and 
the  other  to  the  pure  red  ones.  Such  cases  may 
be  discovered  by  means  of  curves,  but  the  con- 
stituents cannot  be  separated  by  culture-exper- 
iments. 

A  curious  peculiarity  is  afforded  by  half- 
curves.  The  number  of  petals  is  often  seen 
to  vary  only  in  one  direction  from  what  should 
be  expected  to  be  the  mean  condition.  With 
buttercups  and  brambles  and  many  others  there 
is  only  an  increase  above  the  typical  five; 
quaternate  flowers  are  wanting  or  at  least  are 
very  rare.  With  weigelias  and  many  others  the 
number  of  the  tips  of  the  corolla  varies  down- 
wards, going  from  five  to  four  and  three.  Hun- 
dreds of  flowers  show  the  typical  five,  and  de- 
termine the  summit  of  the  curve.  This  drops 
down  on  one  side  only,  indicating  unilateral 
variability,  which  in  many  cases  is  due  to  a 
very  intimate  connection  of  a  concealed  sec- 
ondary summit  and  the  main  one.  In  the 
case  of  the  bulbous  buttercup,  Ranunculus  hul- 
hosus,  I  have  succeeded  in  isolating  this  second- 
ary summit,  although  not  in  a  separate  variety, 
but  only  in  a  form  corresponding  to  the  type 
of  ever-sporting  varieties. 


Laws  of  Fluctuations  741 

Recapitulating  the  results  of  this  too  con- 
densed discussion,  we  may  state  that  fluctua- 
tions are  linear,  being  limited  to  an  increase  and 
to  a  decrease  of  the  characters.  These  changes 
are  mainly  due  to  differences  in  nourishment, 
either  of  the  whole  organism  or  of  its  parts. 
In  the  first  case,  the  deviations  from  the  mean 
are  called  individual;  they  are  of  great  impor- 
tance for  the  hereditary  characters  of  the 
offspring.  In  the  second  case  the  deviations 
are  far  more  universal  and  far  more  striking, 
but  of  lesser  importance.  They  are  called  par- 
tial fluctuations. 

All  these  fluctuations  comply,  in  the  main, 
with  the  law  of  probability,  and  behave  as  if 
their  causes  were  influenced  only  by  chance. 


Lecture  XXVI 

ASEXUAL    MULTIPLICATION    OF    EXTREMES 

Fluctuating  variability  may  be  regarded  from 
two  different  points  of  view.  The  multiformity 
of  a  bed  of  flowers  is  often  a  desirable  feature, 
and  all  means  which  widen  the  range  of  fluctua- 
tion are  therefore  used  to  enhance  this  feature, 
and  variability  affords  specimens,  which  sur- 
pass the  average,  by  yielding  a  better  or  larger 
product. 

In  the  case  of  fruits  and  other  cultivated 
forms,  it  is  of  course  profitable  to  propagate 
from  the  better  specimens  only,  and  if  possible 
only  from  the  very  best.  Obviously  the  best  are 
the  extremes  of  the  whole  range  of  diverging 
forms,  and  moreover  the  extremes  on  one  side  of 
the  group.  Almost  always  the  best  for  practical 
purposes  is  that  in  which  some  quality  is 
strengthened.  Cases  occur  however,  in  which 
it  is  desirable  to  diminish  an  injurious  pecul- 
iarity as  far  as  possible,  and  in  these  instances 
the  opposite  extreme  is  the  most  profitable  one. 

These  considerations  lead  us  to  a  discussion 

742 


Multiplication  of  Extremes  743 

of  the  results  of  the  choice  of  extremes,  which  it 
may  be  easily  seen  is  a  matter  of  the  greatest 
practical  importance.  This  choice  is  generally 
designated  as  selection,  but  as  with  most  of  the 
terms  in  the  domain  of  variability,  the  word 
selection  has  come  to  have  more  than  one  mean- 
ing. Facts  have  accumulated  enormously  since 
the  time  of  Darwin,  a  more  thorough  knowl- 
edge has  brought  about  distinctions,  and  di- 
visions at  a  rapidly  increasing  rate,  with  which 
terminology  has  not  kept  pace.  Selection  in- 
cludes all  kinds  of  choice.  Darwin  distin- 
guished between  natural  and  artificial  selection, 
but  pro]3er  subdivisions  of  these  conceptions  are 
needed. 

In  the  fourth  lecture  we  dealt  with  this  same 
question,  and  saw  that  selection  must,  in  the  first 
place,  make  a  choice  between  the  elementary 
species  of  the  same  systematic  form.  This 
selection  of  species  or  species-selection  was  the 
work  of  Le  Couteur  and  Patrick  Shirretf ,  and  is 
now  in  general  use  in  practice  where  it  has  re- 
ceived the  name  of  variety-testing.  This  clear 
and  unequivocal  term  however,  can  hardly  be 
included  under  the  head  of  natural  selection. 
The  poetic  terminology  of  selection  by  nature 
has  already  brought  about  many  difficulties  that 
should  be  avoided  in  the  future.  On  the  other 
hand,  the  designation  of  the  process  as  a  natural 


744  Fluctuations 

selection  of  species  complies  as  closely  as  possi- 
ble with  existing  terminology,  and  does  not 
seem  liable  to  any  misunderstanding. 

It  is  a  selection  between  species.  Opposed  to 
it  is  the  selection  ivithin  the  species.  Manifest- 
ly the  first  should  precede  the  second,  and  if  this 
sequence  is  not  conscientiously  followed  it  will 
result  in  confusion.  This  is  evident  when  it 
is  considered  that  fluctuations  can  only  appear 
with  their  pure  and  normal  type  in  pure  strains^ 
and  that  each  admixture  of  other  units  is  liable 
to  be  shown  by  the  form  of  the  curves.  More- 
over, selection  chooses  single  individuals,  and  a 
single  plant,  if  it  is  not  a  hybrid,  can  scarcely 
pertain  to  two  different  species.  The  first 
choice  therefore  is  apt  to  make  the  strain  pure. 

In  contrasting  selection  between  species  with 
that  within  the  species,  of  course  elementary 
species  are  meant,  including  varieties.  The 
terms  would  be  of  no  consequence  if  only  right- 
ly understood.  For  the  sake  of  clearness  we 
might  designate  the  last  named  process  with 
the  term  of  intra- specific  selection,  and  it  is 
obvious  that  this  term  is  applicable  both  to 
natural  and  to  artificial  selection. 

Having  previously  dealt  with  species-selec- 
tion at  sufiicient  length,  we  may  now  confine  our- 
selves to  the  consideration  of  the  intra-specific 


Multiplication  of  Extremes  745 

selection-process.  In  practice  it  is  of  secondary 
importance,  and  in  nature  it  takes  a  very  subor- 
dinate position.  For  this  reason  it  will  be  best 
to  confine  further  discussions  to  the  experience 
of  the  breeders. 

Two  different  ways  are  open  to  make  fluctuat- 
ing variability  profitable.  Both  consist  in  the 
multiplication  of  the  chosen  extremes,  and  this 
increase  may  be  attained  in  a  vegetative  man- 
ner, or  by  the  use  of  seeds.  Asexual  and  sexual 
propagation  are  different  in  many  respects,  and 
so  they  are  also  in  the  domain  of  variability. 

In  order  to  obtain  a  clear  comprehension  of 
this  difference,  it  is  necessary  to  start  from  the 
distinction  between  individual  and  partial  fluc- 
tuations, as  given  in  the  last  lecture.  This 
distinction  may  be  discussed  more  understand- 
ingly  if  the  causes  of  the  variability  are  taken 
into  consideration.  We  have  dealt  with  them 
at  some  length,  and  are  now  aware  that  inner 
conditions  only,  determine  averages,  while  some 
fluctuation  around  them  is  allowable,  as  influ- 
enced by  external  conditions.  These  outward 
influences  act  throughout  life.  At  the  very  first 
they  impress  their  stamp  on  the  whole  organism, 
and  incite  a  lasting  change  in  distinct  directions. 
This  is  the  period  of  the  development  of  the 
germ  within  the  seed ;  it  begins  with  the  fusion 
of  the  sexual  cells,  and  each  of  them  may  be  in- 


746  Fluctuations 

fluenced  to  a  noticeable  degree  before  this  union. 
This  is  the  period  of  the  determination  of  indi- 
vidual variability.  As  soon  as  ramifications  be- 
gin, the  external  conditions  act  separately  on 
every  part,  influencing  some  to  a  greater  and 
others  to  a  lesser  degree.  Here  we  have  the 
beginning  of  partial  variability.  At  the  outset 
all  parts  may  be  affected  in  the  same  way  and 
in  the  same  measure,  but  the  chances  of  such  an 
agreement,  of  course,  rapidly  diminish.  This  is 
partly  due  to  differences  in  exposure,  but  main- 
ly to  alterations  of  the  sensibility  of  the  organs 
themselves. 

It  is  difficult  to  gain  a  clear  conception  of  the 
contrast  between  individual  and  partial  varia- 
bility, and  neither  is  it  easy  to  appreciate 
their  cooperation  rightly.  Perhaps  the  best 
way  is  to  consider  their  activity  as  a  gradual 
narrowing  of  possibilities.  At  the  outset  the 
plant  may  develop  its  qualities  in  any  measure, 
nothing  being  as  yet  fixed.  Gradually  how- 
ever, the  development  takes  a  definite  direction, 
for  better  or  for  worse.  Is  a  direction  once 
taken,  then  it  becomes  the  average,  around 
which  the  remaining  possibilities  are  grouped. 
The  plant  or  the  organ  goes  on  in  this  way,  un- 
til finallv  it  reaches  maturitv  with  one  of  the 
thousands  of  degrees  of  development,  between 
which  at  the  beginning  it  had  a  free  choice. 


Multiplication  of  Extremes  747 

Putting  this  discussion  in  other  terms,  we  find 
every  individual  and  every  organ  in  the  adult 
state  corresponding  with  a  single  ordinate  of 
the  curve.  The  curve  indicates  the  range  of 
possibilities,  the  ordinate  shows  the  choice  that 
has  been  made.  Now  it  is  clear  at  once  that 
this  choice  has  not  been  made  suddenly  but 
gradually.  Halfway  of  the  development,  the 
choice  is  halfway  determined,  but  the  other  half 
is  still  undefined.  The  first  half  is  the  same  for 
all  the  organs  of  the  plant,  and  is  therefore 
termed  individual;  the  second  differs  in  the 
separate  members,  and  consequently  is  known  as 
partial.  Which  of  the  two  halves  is  the  greater 
and  which  the  lesser,  of  course  depends  on  the 
cases  considered. 

Finally  we  may  describe  a  single  example,  the 
length  of  the  capsules  of  the  evening-primrose. 
This  is  highly  variable,  the  longest  reaching 
more  than  twice  the  length  of  the  smallest. 
Many  capsules  are  borne  on  the  same  spike, 
and  they  are  easih^  seen  to  be  of  unequal  size. 
They  vary  according  to  their  position,  the 
size  diminishing  in  the  main  from  the  base  up- 
wards, especially  on  the  higher  parts.  Like- 
wise the  fruits  of  weaker  lateral  branches  are 
smaller.  Curves  are  easily  made  by  measuring 
a  few  hundred  capsules  from  corresponding 
parts  of  different  plants,  or  even  by  limiting  tlie 


748  Fluctuations 

inquiry  to  a  single  individual.  These  curves 
give  the  partial  variability,  and  are  found  to 
comply  with  Quetelet  ^s  law. 

Besides  this  limited  study,  we  may  compare 
the  numerous  individuals  of  one  locality  or  of 
a  large  plot  of  cultivated  plants  with  one  an- 
other. In  doing  so,  we  are  struck  with  the  fact 
that  some  plants  have  large  and  others  small 
fruits.  We  now  limit  ourselves  to  the  main 
spike  of  each  plant,  and  perhaps  to  its  lower 
parts,  so  as  to  avoid  as  far  as  possible  the  im- 
pression made  by  the  partial  fluctuations.  The 
differences  remain,  and  are  sufficient  to  fur- 
nish an  easy  comparison  with  the  general  law. 
In  order  to  do  this,  we  take  from  each  plant  a 
definite  number  of  capsules  and  measure  their 
average  length.  In  some  experiments  I  took 
the  twenty  lowermost  capsules  of  the  main 
spikes.  In  this  way  one  average  was  obtained 
for  each  plant,  and  combining  these  into  a  curve, 
it  was  found  that  these  fluctuations  also  came 
under  Quetelet 's  law.  Thus  the  individual  aver- 
ages, and  the  fluctuations  around  each  of  them, 
follow  the  same  rule.  The  first  are  a  measure 
for  the  whole  plant,  the  second  only  for  its  parts. 

As  a  general  resume  we  can  assert  that,  as  a 
rule,  a  quality  is  determined  in  some  degree 
during  the  earlier  stages  of  the  organism,  and 
that  this  determination  is  valid  throughout  its 


Multiplication  of  Extremes  749 

life.  Afterwards  only  the  minor  points  remain 
to  be  regulated.  This  makes  it  at  once  clear 
that  the  range  of  individual  and  partial  vari- 
ability together  must  be  wider  than  that  of 
either  of  them,  taken  alone.  Partial  fluctua- 
tions cannot,  of  course,  be  excluded.  Thus  our 
comparison  is  limited  to  individual  and  partial 
variability  on  one  side,  and  partial  fluctuations 
alone  on  the  other  side. 

Intra-specific  selection  is  thus  seen  to  fall 
under  two  heads:  a  selection  between  the  in- 
dividuals, and  a  choice  within  each  of  them. 
The  first  affords  a  wider  and  the  latter  a  nar- 
rower field. 

Individual  variability,  considered  as  the  re- 
sult of  outward  influences  operative  during  ex- 
treme youth,  can  be  excluded  in  a  very  simple 
manner.  Obviously  it  suffices  to  exclude  ex- 
treme youth,  in  other  words,  to  exclude  the  use 
of  seeds.  Multiplication  in  a  vegetative  way, 
by  grafting  and  budding,  by  runners  or  roots, 
or  by  simple  division  of  rootstocks  and  bulbs  is 
the  way  in  which  to  limit  variability  to  the  par- 
tial half.  This  is  all  we  may  hope  to  attain,  but 
experience  shows  that  it  is  a  very  efficient  means 
of  limitation.  Partial  fluctuations  are  gener- 
ally far  smaller  than  individual  and  partial 
fluctuations  together. 

Individual  variability  in  the  vegetable  king- 


750  Fluctuations 

dom  might  be  called  seed-variation,  as  opposed 
to  partial  or  bud-fluctuation.  And  perhaps  these 
terms  are  more  apt  to  convey  a  clear  conception 
of  the  distinction  than  any  other.  The  germ 
within  the  unripe  seed  is  easily  understood  to 
be  far  more  sensitive  to  external  conditions  than 
a  bud. 

Multiplication  of  extremes  by  seed  is  thus  al- 
ways counteracted  by  individual  variability, 
which  at  once  reopens  all,  or  nearly  all,  the  ini- 
tial possibilities.  Multiplication  by  buds  is  ex- 
empt from  this  danger  and  thus  leads  to  a  high 
degree  of  uniformity.  And  this  uniformity  is  in 
many  cases  exactly  what  the  breeder  endeavors 
to  obtain. 

We  will  treat  of  this  reopening  of  previous 
possibilities  under  the  head  of  regression  in  the 
next  lecture.  It  is  not  at  all  absolute,  at  least 
not  in  one  generation.  Part  of  the  improve- 
ment remains,  and  favors  the  next  generation. 
This  part  may  be  estimated  approximately  as 
being  about  one-third  or  one-half  of  the  im- 
provement attained.  Hence  the  conclusion  that 
vegetative  multiplication  gives  rise  to  varieties 
which  are  as  a  rule  twice  or  thrice  as  good  as 
selected  varieties  of  plants  propagated  by  seeds. 
Hence,  likewise  the  inference  that  breeders  gen- 
erally prefer  vegetative  multiplication  of  im- 
proved forms,  and  apply  it  in  all  possible  cases. 


Multiplication  of  Extremes  751 

Of  course  the  application  is  limited,  and  forage- 
crops  and  the  greater  number  of  vegetables  will 
always  necessarily  be  propagated  by  seed. 

Nature  ordinarily  prefers  the  sexual  way. 
Asexual  multiplications,  although  very  common 
with  perennial  plants,  appear  not  to  otfer  im- 
portant material  for  selection.  Hence  it  fol- 
lows that  in  comparing  the  work  of  nature 
with  that  of  man,  the  results  of  selection  fol- 
lowed by  vegetative  propagation  should  always 
be  carefully  excluded.  Our  large  bulb-flowers 
and  delicious  fruits  have  nothing  in  common 
with  natural  products,  and  do  not  yield  a  stand- 
ard by  which  to  judge  nature's  work. 

It  is  very  difficult  for  a  botanist  to  give  a  sur- 
vey of  what  practice  has  attained  by  the  asexual 
multiplication  of  extremes.  Nearly  all  of  the 
large  and  more  palatable  fruits  are  due  to  such 
efforts.  Some  flowers  and  garden-plants  af- 
ford further  instances.  By  far  the  greatest 
majority  of  improved  asexual  varieties,  how- 
ever, are  not  the  result  of  pure  intra-specific 
selection.  They  are  due  largely  to  the  choice 
of  the  best  existing  elementary  species,  and  to 
some  extent  to  crosses  between  them,  or  be- 
tween distinct  systematic  species.  In  practice 
selection  and  hybridization  go  hand  in  hand  and 
it  is  often  difficult  to  ascertain  what  part  of 


752  Fluctuations 

the  result  is  due  to  the  one,  and  what  to  the 
other  factor. 

The  scientist,  on  the  contrary,  has  nothing  to 
do  with  the  industrial  product.  His  task  is  the 
analysis  of  the  methods,  in  order  to  reach  a 
clear  appreciation  of  the  influence  of  all  the 
competing  factors.  This  study  of  the  working 
causes  leads  to  a  better  understanding  of  the 
practical  processes,  and  may  become  the  basis 
of  improvement  in  methods. 

Starting  from  these  considerations,  we  will 
now  give  some  illustrative  examples,  and  for 
the  first,  choose  one  in  which  hybridization  is 
almost  completely  excluded. 

Sugar-canes  have  long  been  considered  to  be 
plants  without  seed.  Their  numerous  varieties 
are  propagated  only  in  a  vegetative  way.  The 
stems  are  cut  into  pieces,  each  bearing  one 
or  two  or  more  nodes  with  their  buds.  An 
entire  variety,  though  it  may  be  cultivated  in 
large  districts  and  even  in  various  countries,  be- 
haves with  respect  to  variability  as  a  single  in- 
dividual. Its  individual  fluctuability  has  been 
limited  to  the  earliest  period  of  its  life,  when  it 
arose  from  an  unknown  seed.  The  personal 
characters  that  have  been  stamped  on  this  one 
seed,  partly  by  its  descent,  and  partly  in  the  de- 
velopment of  its  germ  during  the  period  of 
ripening,  have  become  the  indelible  characters 


Multiplication  of  Extremes  753 

of  the  variety,  and  only  the  partial  fluctuability, 
due  to  the  effect  of  later  influences,  can  now  be 
studied  statistically. 

This  study  has  for  its  main  object  the  pro- 
duction of  sugar  in  the  stems,  and  the  curves, 
which  indicate  the  percentage  of  this  important 
substance  in  different  stems  of  the  same  variety, 
comply  with  Quetelet's  law.  Each  variety  has 
its  own  average,  and  around  this  the  data  of  the 
majority  of  the  stems  are  densely  crowded, 
while  deviations  on  both  sides  are  rare  and  be- 
come the  rarer  the  wider  they  are.  The  '  *  Cher- 
ibon  ''  cane  is  the  richest  variety  cultivated  in 
Java,  and  has  an  average  of  19^  sugar,  while  it 
fluctuates  between  life  and  28^.  ''  Chunnic  '' 
averages  14^, ''  Black  Manilla''  13f  and  "White 
Manilla ' '  10^ ;  their  highest  and  lowest  extremes 
diverge  in  the  same  manner,  being  for  the  last 
named  variety  If  and  15^. 

This  partial  variability  is  of  high  practical 
interest,  because  on  it  a  selection  may  be  found- 
ed. According  to  the  conceptions  described  in 
a  previous  lecture,  fluctuating  variability  is  the 
result  of  those  outward  factors  that  determine 
the  strength  of  development  of  the  plant  or  the 
organ.  The  inconstancy  of  the  degree  of  sensi- 
bility, combined  with  the  ever-varying  weather- 
conditions  preclude  any  close  proportionality, 
but  apart  from  this  difficulty  there  is,  in  the 


754  Fluctuations 

main,  a  distinct  relation  between  organic 
strength  and  the  development  of  single  qual- 
ities. This  correlation  has  not  escaped  obser- 
vation in  the  case  of  the  sugar-cane,  and  it  is 
known  that  the  best  grown  stocks  are  generally 
the  richest  in  sugar.  Now  it  is  evident  that 
the  best  grown  and  richest  stems  will  have  the 
greater  chance  of  transmitting  these  qualities 
to  the  lateral-buds.  This  at  once  gives  a 
basis  for  vegetative  selection,  upon  which  it  is 
not  necessary  to  choose  a  small  number  of  very 
excellent  stems,  but  simply  to  avoid  the  plant- 
ing of  all  those  that  are  below  the  average.  By 
this  means  the  yield  of  the  cultures  has  often 
noticeably  been  enhanced. 

As  far  as  experience  goes,  this  sort  of  selec- 
tion, however  profitable,  does  not  conduce  to  the 
production  of  improved  races.  Only  temporary 
ameliorations  are  obtained,  and  the  selection 
must  be  made  in  the  same  manner  every  year. 
Moreover  the  improvement  is  very  limited  and 
does  not  give  any  promise  of  further  increase. 
In  order  to  reach  this,  one  has  to  recur  to  the  in- 
dividual fluctuability,  and  therefore  to  seed. 

Nearly  half  a  century  ago,  Parris  discovered, 
on  the  island  of  Barbados,  that  seeds  might 
occasionally  be  gathered  from  the  canes.  These, 
however,  yielded  only  grass-like  plants  of  no 
real  value.     The  same  observation  was  made 


Multiplication  of  Extremes  755 

shortly  afterwards  in  Java  and  in  other  sugar- 
producing  countries.  In  the  year  1885,  Solt- 
wedel,  the  director  of  one  of  the  experiment  sta- 
tions for  the  culture  of  sugar-cane  in  Java, 
conceived  the  idea  of  making  use  of  seedlings 
for  the  production  of  improved  races.  This 
idea  is  a  very  practical  one,  precisely  because  of 
the  possibility  of  vegetative  propagation.  If 
individuals  would  show  the  same  range  as  that 
of  partial  fluctuability,  then  the  choice  of  the 
extremes  would  at  once  bring  the  average  up 
to  the  richness  of  the  best  stocks.  Once  at- 
tained, this  average  would  be  fixed,  without  fur- 
ther efforts. 

Unfortunately  there  is  one  great  drawback. 
This  is  the  infertility  of  the  best  variety,  that 
of  the  ^*  Cheribon  ''  cane.  It  flowers  abun- 
dantly in  some  years,  but  it  has  never  been 
known  to  produce  ripe  seeds.  For  this  reason 
Soltwedel  had  to  start  from  the  second  best  sort, 
and  chose  the  '*  Hawaii  "  cane.  This  variety 
usually  yields  about  14^  sugar,  and  Soltwedel 
found  among  his  seedlings  one  that  showed 
15,1  This  fact  was  quite  unexpected  at  that 
time,  and  excited  widespread  interest  in  the 
new  method,  and  since  then  it  has  been  ap- 
plied to  numerous  varieties,  and  many  thou- 
sands of  seedlings  have  been  raised  and 
tested  as  to  their  sugar-production. 


756  Fluctuations 

From  a  scientific  point  of  view  the  results  are 
quite  striking.  From  the  practical  standpoint, 
however,  the  question  is,  whether  the  ''  Ha- 
waii "  and  other  fertile  varieties  are  adequate 
to  yield  seedlings,  which  will  surpass  the 
infertile  **  Cheribon  ''  cane.  Now  "  Hawaii  " 
averages  14^  and  '' Cheribon  "  W,  and  it 
is  easily  understood  that  a  ^ '  Hawaii  ' '  seed- 
ling with  more  than  19%  can  be  expected 
only  from  very  large  sowings.  Hundreds  of 
thousands  of  seedlings  must  be  cultivated,  and 
their  juice  tested,  before  this  improvement  can 
be  reached.  Even  then,  it  may  have  no  signif- 
icance for  practical  purposes.  Next  to  the 
amount  of  sugar  comes  the  resistance  to  the 
disease  called  ^*  Sereli,"  and  the  new  race 
requires  to  be  ameliorated  in  this  important  di- 
rection, too.  Other  qualities  must  also  be  con- 
sidered, and  any  casual  deterioration  in 
other  characters  would  make  all  progress 
illusory.  For  these  reasons  much  time  is  re- 
quired to  attain  distinct  improvements. 

These  great  difficulties  in  the  way  of  selecting 
extremes  for  vegetative  propagation  are  of 
course  met  with  everywhere.  They  impede  the 
work  of  the  breeder  to  such  a  degree,  that  but 
few  men  are  able  to  surmount  them.  Breeding 
new  varieties  necessitates  the  bending  of  every 
effort  to  this  purpose,  and  a  clear  conception  of 


Multiplication  of  Extremes  757 

the  manifold  aspects  of  this  intricate  problem. 
These  fall  under  two  heads,  the  exigencies  of 
practice,  and  the  physiologic  laws  of  varia- 
bility. Of  course,  only  the  latter  heading  comes 
within  the  limits  of  our  discussion  which  in- 
cludes two  main  points.  First  comes  the  gen- 
eral law  of  fluctuation  that,  though  slight 
deviations  from  the  average  may  be  found 
by  thousands,  or  rather  in  nearly  every  in- 
dividual, larger  and  therefore  important  de- 
viations are  very  rare.  Thousands  of  seedlings 
must  be  examined  carefully  in  order  to  find  one 
or  two  from  which  it  might  be  profitable  to 
start  a  new  race.  This  point  is  the  same 
for  practical  and  for  scientific  investigation. 
In  the  second  place  however,  a  digression 
is  met  with.  The  practical  man  must  take 
into  consideration  all  the  varying  qualities  of 
his  improved  strains.  Some  of  them  must  be 
increased  and  others  be  decreased,  and  their 
common  dependency  on  external  conditions 
often  makes  it  very  difficult  to  discover  the  de- 
sired combinations.  It  is  obvious,  however, 
that  the  neglect  of  one  quality  may  make  all  im- 
provement of  other  characters  wholly  useless. 
No  augmentation  of  sugar-percentage,  of  size 
and  flavor  of  fruits  can  counterbalance  an  in- 
crease in  sensitiveness  to  disease,  and  so  it  is 
with  other  qualities  also. 


758  Fluctuations 

Improved  races  for  scientific  investigation 
can  be  kept  free  from  infection,  and  protected 
against  numerous  other  injuries.  In  the  exper- 
imental garden  they  may  find  conditions  which 
cannot  be  realized  elsewhere.  They  may  show 
a  luxuriant  growth,  and  prove  to  be  excellent 
material  for  research,  but  have  features  which, 
having  been  overlooked  at  the  period  of  selec- 
tion, would  at  once  condemn  them  if  left  to 
ordinary  conditions,  or  to  the  competition  of 
other  species. 

Considering  all  these  obstacles,  it  is  only  nat- 
ural that  breeders  should  use  every  means  to 
reach  their  goal.  Only  in  very  rare  instances 
do  they  follow  methods  analogous  to  scientific 
processes,  which  tend  to  simplify  the  questions 
as  much  as  possible.  As  a  rule,  the  practical 
way  is  the  combination  of  as  many  causes  of 
variability  as  possible.  Now  the  three  great 
sources  of  variability  are,  as  has  been  pointed 
out  on  several  occasions,  the  original  multi- 
fomiity  of  the  species,  fluctuating  variability, 
and  hybridization.  Hence,  in  practical  experi- 
ments, all  three  are  combined.  Together  they 
yield  results  of  the  highest  value,  and  Bur- 
bank's  improved  fruits  and  flowers  give  testi- 
mony to  the  practical  significance  of  this  com- 
bination. 

From  a  scientific  point  of  view  however,  it  is 


Multiplication  of  Extremes  759 

ordinarily  difficult,  if  not  impossible,  to  discern 
the  part  which  each  of  the  three  great  branches 
of  variability  has  taken  in  the  origination  of  the 
product.  A  full  analysis  is  rarely  possible,  and 
the  treatment  of  one  of  the  three  factors  must 
necessarily  remain  incomplete. 

Notwithstanding  these  considerations,  I  will 
now  give  some  examples  in  order  to  show  that 
fluctuating  variability  plays  a  prominent  part  in 
these  improvements.  Of  course  it  is  the  third 
in  importance  in  the  series.  First  comes  the 
choice  of  the  material  from  the  assemblage  of 
species,  elementary  species  and  varieties. 
Hybridization  comes  next  in  importance.  But 
even  the  hybrids  of  the  best  parents  may  be  im- 
proved, because  they  are  no  less  subject  to 
Quetelet's  law  than  any  other  strain.  Any 
large  number  of  hybrids  of  the  same  ancestry 
will  prove  this,  and  often  the  excellency  of  a 
hybrid  variety  depends  chiefly,  or  at  least  defi- 
nitely, on  the  selection  of  the  best  individuals. 
Being  propagated  only  in  a  vegetative  way,  they 
retain  their  original  good  qualities  through  all 
further  culture  and  multiplication. 

As  an  illustrative  example  I  will  take  the 
genus  Canna.  Originally  cultivated  for  its 
large  and  bright  foliage  only,  it  has  since  be- 
come a  flowering  plant  of  value.  Our  garden 
strains   have    originated    by    the    crossing    of 


760  Fluctuations 

a  number  of  introduced  wild  species,  among 
which  the  Canna  indica  is  the  oldest,  now  giv- 
ing its  name  to  the  whole  group.  It  has  tall 
stems  and  spikes  with  rather  inconspicuous 
flowers  with  narrow  petals.  It  has  been  crossed 
with  C.  nepalensis  and  C.  warczewiczii,  and 
the  available  historic  evidence  points  to  the 
vear  1846  as  that  of  the  first  cross.  This  was 
made  by  Annee  between  the  indica  and  the  ne- 
palensis; it  took  ten  years  to  multiply  them  to 
the  required  degree  for  introduction  into  com- 
merce. These  first  hybrids  had  bright  foliage 
and  were  tall  plants,  but  their  flowers  were  by 
no  means  remarkable. 

Once  begun,  hybridization  was  widely  prac- 
ticed. About  the  year  1889  Crozy  exhibited  at 
Paris  the  first  beautifully  flowering  form,  which 
he  named  for  his  wife,  ''  Madame  Crozy." 
Since  that  time  he  and  many  others  have  im- 
proved the  flowers  in  the  shape  and  size,  as  well 
as  in  color  and  its  patterns.  In  the  main, 
these  ameliorations  have  been  due  to  the  discov- 
ery and  introduction  of  new  wild  species  pos- 
sessing the  required  characters.  This  is  illus- 
trated by  the  following  incident.  In  the  year 
1892  I  visited  Mr.  Crozv  at  Lvons.  He  showed 
me  his  nursery  and  numerous  acquisitions,  those 
of  former  years  as  well  as  those  that  were  quite 
new,  and  which  were  in  the  process  of  rapid 


Multiplication  of  Extremes  761 

multiplication,  previous  to  being  given  to  the 
trade.  I  wondered,  and  asked,  why  no  pure 
white  variety  was  present.  His  answer  was: 
^^  Because  no  white  species  had  been  found  up 
to  the  present  time,  and  there  is  no  other  means 
of  producing  white  varieties  than  by  crossing 
the  existing  forms  with  a  new  white  type. ' ' 

Comparing  the  varieties  produced  in  succes- 
sive periods,  it  is  very  easy  to  appreciate  their 
gradual  improvement.  On  most  points  this  is 
not  readily  put  into  words,  but  the  size  of  the 
petals  can  be  measured,  and  the  figures  may 
convey  at  least  some  idea  of  the  real  state  of 
things.  Leaving  aside  the  types  with  small 
flowers  and  cultivated  exclusively  for  their 
foliage,  the  oldest  flowers  of  Canna  had 
petals  of  45  mm.  length  and  13  mm.  breadth. 
The  ordinary  types  at  the  time  of  my  visit  had 
reached  61  by  21  mm.,  and  the  ''  Madame 
Crozy  ' '  showed  ^^  by  30  mm.  It  had  however, 
already  been  surpassed  by  a  few  commercial  va- 
rieties, which  had  the  same  length  but  a  breadth 
of  35  mm.  And  the  latest  production,  which 
required  some  years  of  propagation  before  be- 
ing put  on  the  market,  measured  83  by  43  mm. 
Thus  in  the  lapse  of  some  thirty  years  the  length 
had  been  doubled  and  the  breadth  tripled,  giv- 
ing flowers  with  broad  corollas  and  with  petals 


762  Fluctuations 

joined  all  around,  resembling  the  best  types  of 
lilies  and  amarvllis. 

%■' 

Striking  as  this  result  unquestionably  is,  it 
remains  doubtful  as  to  what  part  of  it  is  due  to 
the  discovery  and  introduction  of  new  large 
flowered  species,  and  what  to  the  selection  of 
the  extremes  of  fluctuating  variability.  As  far 
as  I  have  been  able  to  ascertain  however,  and 
according  to  the  evidence  given  to  me  by  Mr. 
Crozy,  selection  has  had  the  largest  part  in  re- 
gard to  the  size,  while  the  color-patterns  are 
introduced  qualities. 

The  scientific  analysis  of  other  intricate  ex- 
amples is  still  more  difficult.  To  the  practical 
breeder  they  often  seem  very  simple,  but  the 
student  of  hereditv,  who  wishes  to  discern  the 
different  factors,  is  often  quite  puzzled  by  this 
apparent  simplicity.  So  it  is  in  the  case  of 
the  double  lilacs,  a  large  number  of  varieties  of 
which  have  recently  been  originated  and  intro- 
duced into  commerce  by  Lemoine  of  Nancy.  In 
the  main  they  owe  their  origin  to  the  crossing 
and  recrossing  of  a  single  plant  of  the  old 
double  variety  with  the  numerous  existing 
single-flowered  sorts. 

This  double  variety  seems  to  be  as  old  as  the 
culture  of  the  lilacs.  It  was  already  known  to 
Hunting,  who  described  it  in  the  year  1671. 
Two  centuries  afterwards,  in  1870,  a  new  de- 


Mult  i  plication  of  Ext  rem  cs  763 

scription  was  given  by  Morren,  and  though 
more  than  one  varietal  name  is  recorded  in  his 
paper,  it  appears  from  the  facts  given  that  even 
at  that  time  only  one  variety  existed.  It  was 
commonly  called  Syringa  vulgaris  azurea 
plena,  and  seems  to  have  been  very  rare  and 
without  real  ornamental  value. 

Lemoine,  however,  conceived  the  desirability 
of  a  combination  of  the  doubling  with  the  bright 
colors  and  large  flower-racemes  of  other  lilacs, 
and  performed  a  series  of  crosses.  The 
'^  azurea  plena  '^  has  no  stamens,  and  therefore 
must  be  used  in  all  crosses  as  the  pistil-parent ; 
its  ovary  is  narrowly  inclosed  in  the  tube  of  the 
flower,  and  difficult  to  fertilize.  On  the  other 
hand,  new  crosses  could  be  made  every  year, 
and  the  total  number  of  hvbrids  with  differ- 
ent  pollen-parents  was  rapidly  increased. 
After  five  years  the  hybrids  began  to  flower  and 
could  be  used  for  new  crosses,  yielding  a  series 
of  compound  hybrids,  which  however,  were  not 
kept  separate  from  the  products  of  the  first 
crosses. 

Gradually  the  number  of  the  flowering  speci- 
mens increased,  and  the  character  of  doubling 
was  observed  to  be  variable  to  a  high  degree. 
Sometimes  only  one  supernumerary  petal  was 
produced,  sometimes  a  whole  new  typical  corolla 
was  extruded  from  within  the  first.    In  the  same 


764  Fluctuations 

way  the  color  and  the  number  of  the  flowers  on 
each  raceme  were  seen  to  vary.  Thousands  of 
hybrids  were  produced,  and  only  those  which 
exhibited  real  advantages  were  selected  for 
trade.  These  were  multiplied  by  grafting,  and 
each  variety  at  present  consists  only  of  the  buds 
of  one  original  individual  and  their  products. 
No  constancy  from  seed  is  assumed,  many 
varieties  are  even  quite  sterile. 

Of  course,  no  description  was  given  of  the  re- 
jected forms.  It  is  only  stated  that  many  of 
them  bore  either  single  or  poorly  filled  flow- 
ers, or  were  objectionable  in  some  other  way. 
The  range  of  variability,  from  which  the  choices 
were  made,  is  obscure  and  only  the  fact  of  the 
selection  is  prominent.  What  part  is  due  to 
the  combination  of  the  parental  features  and 
what  to  the  individual  fluctuation  of  the  hybrid 
itself  cannot  be  ascertained. 

So  it  is  in  numerous  other  instances.  The 
dahlias  have  been  derived  from  three  or  more 
original  species,  and  been  subjected  to  cultiva- 
tion and  hybridization  in  an  ever-increasing 
scale  for  a  century.  The  best  varieties  are  only 
propagated  in  the  vegetative  way,  by  the  roots 
and  buds,  or  by  grafting  and  cutting.  Each  of 
them  is,  with  regard  to  its  hereditary  qualities, 
only  one  individual,  and  the  individual  charac- 
ters were  selected  at  the  same  time  with  the 


Multiplication  of  Extremes  765 

varietal  and  hybrid  characters.  Most  of  them 
are  very  inconstant  from  seed  and  as  a  rule, 
only  mixtures  are  offered  for  sale  in  seed-lists. 
Which  of  their  ornamental  features  are  due  to 
fluctuating  deviation  from  an  average  is  of 
course  unknown.  Amaryllis  and  Gladiolus  are 
surrounded  with  the  same  scientific  uncertain- 
ties. Eight  or  ten,  or  even  more,  species  have 
heen  combined  into  one  large  and  multiform 
strain,  each  bringing  its  peculiar  qualities  into 
the  mixed  mass.  Every  hybrid  variety  is  one 
individual,  being  propagated  by  bulbs  only. 
Colors  and  color-patterns,  shape  of  petals  and 
other  marks,  have  been  derived  from  the  wild 
ancestors,  but  the  large  size  of  many  of  the  best 
varieties  is  probably  due  to  the  selection  of  the 
extremes  of  fluctuating  variability.  So  it  is 
with  the  begonias  of  our  gardens,  which  are 
also  composite  hybrids,  but  are  usually  sown 
on  a  very  large  scale.  Flowers  of  15  cm.  diam- 
eter are  very  showy,  but  there  can  be  no  doubt 
about  the  manner  in  which  they  are  produced, 
as  the  wild  species  fall  far  short  of  this  size. 

Among  vegetables  the  potatoes  afford  an- 
other instance.  Originally  quite  a  number  of 
good  species  were  in  culture,  most  of  them  hav- 
ing small  tubers.  Our  present  varieties  are  due 
to  hvbridization  and  selection,  each  of  them 
being  propagated  only  in  the  vegetative  way. 


766  Fluctuations 

Selection  is  founded  upon  different  qualities,  ac- 
cording to  the  use  to  be  made  of  the  new  sort. 
Potatoes  for  the  factory  have  even  been  selected 
for  their  amount  of  starch,  and  in  this  case  at 
least,  fluctuating  variability  has  played  a  very 
important  part  in  the  improvement  of  the  race. 

Vegetative  propagation  has  the  great  advan- 
tage of  exempting  the  varieties  from  regression 
to  mediocrity,  which  always  follows  multiplica- 
tion by  seeds.  It  affords  the  possibility  of  keep- 
ing the  extremes  constant,  and  this  is  not  its 
only  advantage.  Another,  likewise  highly  in- 
teresting, side  of  tlie  question  is  the  uniformity 
of  the  whole  strain.  This  is  especially  im- 
portant in  the  case  of  fruits,  though  ordinarily 
it  is  regarded  as  a  matter  of  course,  but  there 
are  some  exceptions  which  give  proof  of  the 
real  importance  of  the  usual  condition.  For  ex- 
ample, the  walnut-tree.  Thousands  of  acres  of 
walnut-orchards  consist  of  seedling  trees 
grown  from  nuts  of  unknown  parentage.  The 
result  is  a  great  diversity  in  the  types  of  trees 
and  in  the  size  and  shape  of  the  nuts,  and  this 
diversity  is  an  obvious  disadvantage  to  the  in- 
dustry. The  cause  lies  in  the  enormous  diffi- 
culties attached  to  grafting  or  budding  of  these 
trees,  which  make  this  method  very  expensive 
and  to  a  high  degree  uncertain  and  unsatis- 
factory. 


Multiplication  of  Extremes  767 

After  this  hasty  survey  of  the  more  reliable 
facts  of  the  practice  of  an  asexual  multiplica- 
tion of  the  extremes  of  fluctuating  variability, 
we  may  now  return  to  the  previously  mentioned 
theoretical  considerations.  These  are  con- 
cerned with  an  estimation  of  the  chances  of  the 
occurrence  of  deviations,  large  enough  to  ex- 
hibit commercial  value.  This  chance  may  be 
calculated  on  the  basis  of  Quetelet's  law, 
whenever  the  agreement  of  the  fluctuation  of  the 
qualit}^  under  consideration  has  been  empiric- 
ally determined.  In  the  discussion  of  the  meth- 
ods of  comparing  two  curves,  we  have  pointed 
to  the  quartiles  as  the  decisive  points,  and  to 
the  necessity  of  drawing  the  curves  so  that  these 
points  are  made  to  overlie  one  another,  on 
each  side  of  the  average.  If  now  we  calculate 
the  binomium  of  Newton  for  different  values  of 
the  exponent,  the  sum  of  the  coefficients  is 
doubled  for  each  higher  unit  of  the  exponent, 
and  at  the  same  time  the  extreme  limit  of  the 
curve  is  extended  one  step  farther.  Hence  it  is 
possible  to  calculate  a  relation  between  the 
value  of  the  extreme  and  the  number  of  cases 
required.  It  would  take  us  too  long  to  give  this 
calculation  in  detail,  but  it  is  easily  seen  that 
for  each  succeeding  step  the  number  of  individ- 
uals must  be  doubled,  though  the  length  of  the 
steps,  or  the  amount  of  increase  of  the  quality 


768  Fluctuations 

remains  the  same.  The  result  is  that  many- 
thousands  of  seedlings  are  required  to  go  be- 
yond the  ordinary  range  of  variations,  and  that 
every  further  improvement  requires  the  doub- 
ling of  the  whole  culture.  If  ten  thousand  do 
not  give  a  profitable  deviation,  the  next  step  re- 
quires twenty  thousand,  the  following  forty 
thousand,  and  so  on.  And  all  this  work  would 
be  necessary  for  the  improvement  of  a  single 
quality,  while  practice  requires  the  examination 
and  amelioration  of  nearly  all  the  variable 
characters  of  the  strain. 

Hence  the  rule  that  great  results  can  only  be 
obtained  by  the  use  of  large  numbers,  but  it  is 
of  no  avail  to  state  this  conclusion  from  a  scien- 
tific point  of  view.  Scientific  experimenters 
will  rarely  be  able  to  sacrifice  fifty  thousand 
plants  to  a  single  selection.  The  problem  is  to 
introduce  the  principle  into  practice  and  to 
prove  its  direct  usefulness  and  reliability.  It  is 
to  Luther  Burbank  that  we  owe  this  great 
achievement.  His  principles  are  in  full  har- 
mony with  the  teachings  of  science.  His  meth- 
ods are  hybridization  and  selection  in  the 
broadest  sense  and  on  the  largest  scale.  One 
very  illustrative  example  of  his  methods  must 
suffice  to  convey  an  idea  of  the  work  necessary 
to  produce  a  new  race  of  superlative  excel- 
lency.    Forty  thousand  blackberry  and  rasp- 


Multiplication  of  Extremes  769 

berry  hybrids  were  produced  and  grown 
until  the  fruit  matured.  Then  from  the  whole 
lot  a  single  variety  was  chosen  as  tlie  best. 
It  is  now  known  under  the  name  of  ''  Paradox.'^ 
All  others  were  uprooted  with  their  crop  of 
ripening  berries,  heaped  up  into  a  pile  twelve 
feet  wide,  fourteen  feet  high  and  twenty-two 
feet  long,  and  burned.  Nothing  remained  of 
that  expensive  and  lengthy  experiment,  except 
the  one  parent-plant  of  the  new  variety.  Sim- 
ilar selections  and  similar  amount  of  work  have 
produced  the  famous  plums,  the  brambles  and 
the  blackberries,  the  Shasta  daisy,  the  peach- 
almond,  the  improved  blueberries,  the  hybrid 
lilies,  and  the  many  other  valuable  fruits  and 
garden-flowers  that  have  made  the  fame  of  Bur- 
bank  and  the  glory  of  horticultural  California. 


Lecture  XXVII 

INCONSTANCY  OF  IMPROVED  RACES 

The  greater  advantages  of  the  asexual  multi- 
plication of  extremes  are  of  course  restricted  to 
perennial  and  woody  plants.  Annual  and  bi- 
ennial species  cannot  as  a  rule,  be  propagated 
in  this  way,  and  even  with  some  perennials  hor- 
ticulturists prefer  the  sale  of  seeds  to  that  of 
roots  and  bulbs.  In  all  these  cases  it  is  clear 
that  the  exclusion  of  the  individual  variability, 
which  was  shown  to  be  an  important  point  in 
the  last  lecture,  must  be  sacrificed. 

Seed-propagation  is  subject  to  individual  as 
well  as  to  fluctuating  variability.  The  first 
could  perhaps  be  designated  by  another  term, 
embryonic  variability,  since  it  indicates  the 
fluctuations  occurring  during  the  period  of 
development  of  the  germ.  This  period  begins 
with  the  fusion  of  the  male  and  female  elements 
and  is  largely  dependent  upon  the  vigor  of  these 
cells  at  the  moment,  and  on  the  varying  qualities 
they  may  have  acquired.  It  comprises  in  the 
main  the  time  of  the  ripening  of  the  seed,  and 

770 


Inconstancy  of  Improved  Races        771 

might  perhaps  best  be  considered  to  end  with 
the  beginning  of  the  resting  stage  of  the  ripe 
seed.  Hence  it  is  clear  that  the  variability  of 
seed-propagated  annual  races  has  a  wider  range 
than  that  of  perennials,  shrubs  and  trees.  At 
present  it  is  difficult  to  discern  exactly  the  part 
each  of  these  two  main  factors  plays  in  the 
process.  Many  indications  are  found  however, 
that  make  it  probable  that  embryonic  variability 
is  wider,  and  perhaps  of  far  greater  impor- 
tance than  the  subsequent  partial  fluctuations. 
The  high  degree  of  similarity  between  the  single 
specimens  of  a  vegetative  variety,  and  the  large 
amount  of  variability  in  seed-races  strongly 
supports  this  view.  The  propagation  and  multi- 
plication of  the  extremes  of  fluctuating  varia- 
bility by  means  of  seeds  requires  a  close 
consideration  of  the  relation  between  seedling 
and  parent.  The  easiest  way  to  get  a  clear  con- 
ception of  this  relation  is  to  make  use  of  the 
ideas  concerning  the  dependency  of  variability 
upon  nourishment.  Assuming  these  to  be  cor- 
rect in  the  main,  and  leaving  aside  all  minor 
questions,  we  may  conclude  that  the  chosen 
extreme  individual  is  one  of  the  best  nourished 
and  intrinsically  most  vigorous  of  the  whole 
culture.  On  account  of  these  very  qualities  it 
is  capable  of  nourishing  all  of  its  organs  bettor 
and  also  its  seeds.     In  other  words,  the  seeds 


772  Fluctuations 

of  the  extreme  individuals  have  exceptional 
chances  of  becoming  better  nourished  than  the 
average  of  the  seeds  of  the  race.  Applying  the 
same  rule  to  them,  it  is  easily  understood  that 
they  will  vary,  by  reason  of  this  better  nourish- 
ment, in  a  direction  corresponding  to  that  of 
their  parent. 

This  discussion  gives  a  very  simple  explana- 
tion of  the  acknowledged  fact  that  the  seeds  of 
the  extremes  are  in  the  main  the  best  for  the 
propagation  of  the  race.  It  does  not  include 
however,  all  the  causes  for  this  preferment. 
Some  are  of  older  date  and  due  to  previous  in- 
fluences. 

A  second  point  in  our  discussion  is  the  appre- 
ciation of  the  fact  that  a  single  individual 
may  be  chosen  to  gather  the  seed  from,  and  that 
these  seeds,  and  the  young  plants  they  yield,  are 
as  a  rule,  numerous.  Hence  it  follows  that  we 
are  to  compare  their  average  and  their  ex- 
tremes with  the  qualities  of  the  parents.  Both 
are  of  practical  as  well  as  of  theoretical  inter- 
est. The  average  of  the  progeny  is  to  be  con- 
sidered as  the  chief  result  of  the  selection  in 
the  previous  generation,  while  the  extremes,  at 
least  those  which  depart  in  the  same  direction, 
are  obviously  the  means  of  further  improve- 
ment of  the  race. 

Thus  our  discussion  should  be  divided  into 


Inconstancy  of  Improved  Races        ll'd 

two  heads.  One  of  these  comprises  the  rela- 
tion of  the  average  of  the  progeny  to  the  excep- 
tional qualities  of  the  chosen  parent,  and  the 
other  the  relation  of  exceptional  offspring  to 
the  exceptional  parents. 

Let  us  consider  the  averages  first.  Are  they 
to  be  expected  to  be  equal  to  the  unique  quality 
of  the  parent,  or  perhaps  to  be  the  same  as  the 
average  of  the  whole  unselected  race?  Neither 
of  these  cases  occur.  Experience  is  clear  and 
definite  on  this  important  point.  Vilmorin, 
when  making  the  first  selections  to  improve  the 
amount  of  sugar  in  beets,  was  struck  with  the 
fact  that  the  average  of  the  progeny  lies  be- 
tween that  of  the  original  strain  and  the  qual- 
ity of  the  chosen  parent.  He  expressed  his  ob- 
servation by  stating  that  the  progeny  are 
grouped  around  and  diverge  in  all  directions 
from  some  point,  placed  on  the  line  which  unites 
their  parent  with  the  type  from  which  it  sprang. 
All  breeders  agree  on  this  point,  and  in  scien- 
tific experiments  it  has  often  been  confirmed. 
We  shall  take  up  some  illustrative  examples 
presently,  but  in  order  to  make  them  clear,  it  is 
necessary  to  give  a  closer  consideration  to  the 
results  of  Vilmorin. 

From  his  experience  it  follows  that  the  aver- 
age of  the  progeny  is  higher  than  that  of  the 
race  at  large,  but  lower  than  the  chosen  parent. 


:'7 


774  Fluctuations 

In  other  words,  there  is  a  progression  and  a  re- 
gression. A  progression  in  relation  to  the  whole 
race,  and  a  regression  in  comparison  with  the 
parent.  The  significance  of  this  becomes  clear 
at  once,  if  we  recall  the  constancy  of  the  variety 
which  could  be  obtained  from  the  selected  ex- 
treme in  the  case  of  vegetative  multiplication. 
The  progression  is  what  the  breeder  wants,  the 
regression  what  he  detests.  Regression  is  the 
permanency  of  part  of  the  mediocrity  which 
the  selection  was  invoked  to  overcome.  Mani- 
festly it  is  of  the  highest  interest  that  the  pro- 
gression should  be  as  large,  and  the  regression 
as  small  as  possible.  In  order  to  attain  this 
goal  the  first  question  is  to  know  the  exact  meas- 
ure of  progression  and  regression  as  they  are 
exhibiting  themselves  in  the  given  cases,  and 
the  second  is  to  inquire  into  the  influences,  on 
which  this  proportion  may  be  incumbent. 

At  present  our  notions  concerning  the  first 
point  are  still  very  limited  and  those  concern- 
ing the  second  extremely  vague.  Statistical  in- 
quiries have  led  to  some  definite  ideas  about  the 
importance  of  regression,  and  these  furnish  a 
basis  for  experimental  researches  concerning 
the  causes  of  the  phenomenon.  Very  ad- 
vantageous material  for  the  study  of  pro- 
gression and  regression  in  the  realm  of 
fluctuating    variability    is     afforded    by    the 


Inconstancy  of  Improved  Races        lib 

ears  of  corn  or  maize.  The  kernels  are  ar- 
ranged in  longitudinal  rows,  and  these  rows  are 
observed  to  occur  in  varying,  but  always  even, 
numbers.  This  latter  circumstance  is  due  to  the 
fact  that  each  two  neighboring  rows  contain 
the  lateral  branches  of  a  single  row  of  spikelets, 
the  axes  of  which  however,  are  included  in  the 
fleshy  body  of  the  ear.  The  variation  of  the 
number  of  the  rows  is  easily  seen  to  comply  with 
Quetelet's  law,  and  often  30  or  40  ears  suf- 
fice to  give  a  trustworthy  curve.  Fritz  Miil- 
ler  made  some  experiments  upon  the  inheritance 
of  the  number  of  the  rows,  in  Brazil.  He  chose 
a  race  which  averaged  12  rows,  selected 
ears  with  14,  16  and  18  rows,  etc.,  and  sowed 
their  kernels  separately.  In  each  of  these  cul- 
tures he  counted  the  rows  of  the  seeds  on  the 
ears  of  all  the  plants  when  ripe,  and  calculated 
their  average.  This  average,  of  course,  does 
not  necessarily  correspond  to  a  whole  number, 
and  fractions  should  not  be  neglected. 

According  to  Vilmorin's  rule  he  always  found 
some  progression  of  the  average  and  some  re- 
gression. Both  were  the  larger,  the  more  the 
parent-ear  differed  from  the  general  average, 
but  the  proportion  between  both  remained  the 
same,  and  seems  independent  of  the  amount  of 
the  deviation.  Putting  the  deviation  at  5, 
the  progression  calculated  from  his  figures  is 


776  Fluctuations 

2  and  the  regression  3.  In  other  words  the  av- 
erage of  the  progeny  has  gained  over  the  aver- 
age of  the  original  variety  slightly  more  than 
one-third,  and  slightly  less  than  one-half  of  the 
parental  deviation.  I  have  repeated  this  exper- 
iment of  Fritz  Miiller's  and  obtained  nearlv  the 
same  regression  of  three-fifths,  though  working 
with  another  variety,  and  under  widely  different 
climatic  conditions. 

The  figures  of  Fritz  Miiller  were,  as  given  be- 
low, in  one  experiment.  In  the  last  column  I 
put  the  improvement  calculated  for  a  propor- 
tion of  two-fifths  above  the  initial  average  of  12. 


Rows  on 
parent  ears 

Average  of  rows 
of  progeny 

12   +    ^    of 

Difference 

u 

12.6 

12.8 

16 

14.1 

13.6 

18 

15.2 

14.4 

20 

15.8 

15.2 

22 

16.1 

16.0 

Gralton,  in  his  work  on  natural  inheritance, 
describes  an  experiment  with  the  seeds  of  the 
sweet  pea  or  Lathyrus  odoratus.  He  deter- 
mined the  average  size  in  a  lot  of  purchased 
seeds,  and  selected  groups  of  seeds  of  differ- 
ent, but  for  each  group  constant,  sizes.  These 
were  sown,  and  the  average  of  the  seeds  was 
determined  anew  in  the  subsequent  harvest  they 
yielded.  These  figures  agreed  with  the  rule  of 
Vilmorin  and  were  calculated  in  the  manner 


Inconstancy  of  Improved  Races        111 

given  for  the  test  of  the  corn.  The  progression 
and  regression  were  found  to  be  proportionate 
to  the  amount  of  the  deviation.  The  progres- 
sion of  the  average  was  one-third,  and  the  re- 
gression in  consequence  two-thirds  of  the  total 
deviation.  The  amelioration  is  thus  seen  to  be 
nearly,  though  not  exactly,  the  same  as  in  the 
previous  case. 

From  the  evidence  of  the  other  correspond- 
ing experiments,  and  from  various  statistical 
inquiries  it  seems  that  the  value  of  the  pro- 
gression is  nearly  the  same  in  most  cases,  irre- 
spective of  the  species  used  and  the  quality  con- 
sidered. It  may  be  said  to  be  from  one-third  to 
one-half  of  the  parental  deviation,  and  in  this 
form  the  statement  is  obviously  of  wide  and 
easy  applicability. 

Our  figures  also  demonstrate  the  great  pre- 
eminence of  vegetative  varieties  above  the  im- 
proved strains  multiplied  by  seeds.  They  have 
a  definite  relation.  Asexually  multiplied 
strains  may  be  said  to  be  generally  two  times 
or  even  three  times  superior  to  the  com- 
mon offspring.  This  is  a  difference  of  great 
practical  importance,  and  should  never  be  lost 
sight  of  in  theoretical  considerations  of  the  pro- 
ductive capacity  of  selection.  Multiplication  by 
seed  however,  has  one  great  advantage  over 
the  asexual  method ;  it  may  be  repeated.     The 


778  Fluctuations 

selection  is  not  limited  to  a  single  choice,  but 
may  be  applied  in  two  or  more  succeeding  gen- 
erations. Obviously  such  a  repetition  affords 
a  better  chance  of  increasing  the  progression  of 
the  average  and  of  ameliorating  the  race  to  a 
greater  degree  than  would  be  possible  by  a  sin- 
gle choice.  This  principle  of  repeated  selection 
is  at  present  the  prominent  feature  of  race- 
improvement.  Next  to  variety-testing  and 
hybridizing  it  is  the  great  source  of  the  steady 
progression  of  agricultural  crops.  From  a 
practical  standpoint  the  method  is  clear  and  as 
perfect  as  might  be  expected,  but  this  is  not  the 
side  of  the  problem  with  which  we  are  concerned 
here.  The  theoretical  analysis  and  explana- 
tion of  the  results  obtained,  however,  is  sub- 
ject to  much  doubt,  and  to  a  great  divergence 
of  conceptions.  So  it  is  also  with  the  applica- 
tion of  the  practical  processes  to  those  occur- 
ring in  nature.  Some  assume  that  here  repeated 
selection  is  only  of  subordinate  importance, 
while  others  declare  that  the  whole  process  of 
evolution  is  due  to  this  agency.  This  very  im- 
portant point  however,  will  be  reserved  for  the 
next  lecture,  and  only  the  facts  available  at  pres- 
ent will  be  considered  here. 

As  a  first  example  we  may  take  the  ray-florets 
of  the  composites.  On  a  former  occasion  we 
have  dealt  with  their  fluctuation  in  number  and 


Inconstancy  of  Improved  Races        11^ 

found  that  it  is  highly  variable  and  complies  in 
the  main  with  Qnetelet's  law.  Madia  elegans, 
a  garden-species,  has  on  the  average  21  rays 
on  each  head,  fluctuating  between  16  and  25  or 
more.    I  saved  the  seeds  of  a  plant  with  only 

17  rays  on  the  terminal  head,  and  got  from 
them  a  culture  which  averaged  19  rays,  which 
is  the  mean  between  21  and  17.  In  this  second 
generation  I  observed  the  extremes  to  be  22  and 
12,  and  selected  a  plant  with  13  rays  as  the 
parent  for  a  continuation  of  the  ex})eriment. 
The  plants,  which  I  got  from  its  seeds,  averaged 

18  and  showed  22  and  13  as  extremes.  The  total 
progression  of  the  average  was  thus,  in  two  gen- 
erations, from  21  to  18,  and  the  total  regression 
from  13  to  18,  and  the  proportion  is  thus  seen 
to  diminish  by  the  repetition  rather  than  to  in- 
crease. 

This  experiment,  however,  is  of  course  too 
imperfect  upon  which  to  found  general  conclu- 
sions. It  only  proves  the  important  fact  that 
the  improved  average  of  the  second  generation 
is  not  the  starting-point  for  the  further  un- 
provement.  But  the  second  generation  allows  a 
choice  of  an  extreme,  which  diverges  noticeably 
more  from  the  mean  than  any  individual  of  the 
first  culture,  and  thereby  gives  a  larger  amount 
of  absolute  progression,  even  if  the  proportion 
between   progression   and   regression   remains 


780  Fluctuations 

the  same.  The  repetition  is  only  an  easy  meth- 
od of  getting  more  widely  deviating  extremes ; 
whether  it  has,  besides  this,  another  effect,  re- 
mains doubtful.  In  order  to  be  able  to  decide 
this  question,  it  is  necessary  to  repeat  the  selec- 
tion during  a  series  of  generations.  In  this 
way  the  individual  faults  may  be  removed  as 
far  as  possible.  I  chose  an  experiment  of  Fritz 
Miiller,  relating  to  the  number  of  rows  of 
grains  on  the  ears  exactly  as  in  the  case  above 
referred  to,  and  which  I  have  repeated  in  my 
experimental  garden  at  Amsterdam. 

I  started  from  a  variety  known  to  fructify 
fairly  regularly  in  our  climate,  and  exhibiting 
in  the  mean  12  - 14  rows,  but  varying  between  8 
and  20  as  exceptional  cases.  I  chose  an  ear 
with  16  rows  and  sowed  its  seeds  in  1887.  A 
number  of  plants  were  obtained,  from  each  of 
which,  one  ear  was  chosen  in  order  to  count  its 
rows.  An  average  of  15  rows  was  found  with 
variations  complying  with  Quetelet's  law.  One 
ear  reached  22  rows,  but  had  not  been  fertilized, 
some  others  had  20  rows,  and  the  best  of  these 
was  chosen  for  the  continuation  of  the  experi- 
ment. I  repeated  the  sowing  during  6  subse- 
quent generations  in  the  same  way,  choosing 
each  time  the  most  beautiful  ear  from  among 
those  with  the  greatest  number  of  rows.  Un- 
fortunately with  the  increase  of  the  number  the 


Inconstancy  of  Improved  Races        781 

size  of  the  grains  decreases,  the  total  amount 
of  nourishment  available  for  all  of  them 
remaining  about  the  same.  Thus  the 
kernels  and  consequently  the  new  plants  be- 
came smaller  and  weaker,  and  the  chance 
of  fertilization  was  diminished  in  the  ears 
with  the  highest  number  of  rows.  Conse- 
quently the  choice  was  limited,  and  after  having 
twice  chosen  a  spike  with  20  and  once  one  with 
24  rows,  I  finally  preferred  those  with  the  inter- 
mediate number  of  22. 

This  repeated  choice  has  brought  the  aver- 
age of  my  race  up  from  13  to  20,  and  thus  to  the 
extreme  limit  of  the  original  variety.  Seven 
years  were  required  to  attain  this  result,  or  on 
an  average  the  progression  was  one  row  in  a 
year.  This  augmentation  was  accompanied  by 
an  accompanying  movement  of  the  whole  group 
in  the  same  direction.  The  extreme  on  the  side 
of  the  small  numbers  came  up  from  8  to  12 
rows,  and  cobs  with  8  or  10  rows  did  not  appear 
in  my  race  later  than  the  third  generation.  On 
the  other  side  the  extreme  reached  28,  a  figure 
never  reached  by  the  original  variety  as  culti- 
vated with  us,  and  ears  with  24  and  26  rows 
have  been  seen  during  the  four  last  generations 
in  increasing  numbers. 

This  slow  and  gradual  amelioration  was  part- 
ly due  to  the  mode  of  pollination  of  the  corn. 


782  Fluctuations 

The  pollen  falls  from  the  male  spikes  on  the 
ears  of  the  same  plant,  but  also  is  easily  blown 
on  surrounding  spikes.  In  order  to  get  the 
required  amount  of  seed  it  is  necessary  in  our 
climate  to  encroach  as  little  as  possible  upon 
free  pollination,  aiding  the  self-pollination, 
but  taking  no  precautions  against  intercross- 
ing. It  is  assumed  that  the  choice  of  the  best 
ears  indicates  the  plants  which  have  had  the 
best  pollen-parents  as  well  as  the  best  pistil- 
parents,  and  that  selection  here,  as  in  other 
cases,  corrects  the  faults  of  free  intercrossing. 
But  it  is  granted  that  this  correction  is  only  a 
slow  one,  and  accounts  in  a  great  degree  for  the 
slowness  of  the  progression.  Under  better  cli- 
matic conditions  and  with  a  more  entire  isola- 
tion of  the  individuals,  it  seems  very  probable 
that  the  same  result  could  have  been  reached 
in  fewer  generations. 

However  this  may  be,  the  fact  is  that  by  re- 
peated selection  the  strain  can  be  ameliorated 
to  a  greater  extent  than  by  a  single  choice.  This 
result  completely  agrees  with  the  general  expe- 
rience of  breeders  and  the  example  given 
is  only  an  instance  of  a  universal  rule.  It  has 
the  advantage  of  being  capable  of  being  re- 
corded in  a  numerical  way,  and  of  allowing  a 
detailed  and  definite  description  of  all  the  suc- 
ceeding generations.    The  entire  harvest  of  all 


Inconstancy  of  Improved  Races        783 

of  them  has  been  counted  and  the  figures  com- 
bined into  curves,  which  at  once  show  the  whole 
course  of  the  pedigree-experiment.  These 
curves  have  in  the  main  taken  the  same  shape, 
and  have  only  gradually  been  moved  in  the 
chosen  direction. 

Three  points  are  now  to  be  considered  in 
connection  with  this  experiment.  The  first  is 
the  size  of  the  cultures  required  for  the  result- 
ing amelioration.  In  other  words,  would  it  have 
been  possible  to  attain  an  average  of  20  rows 
in  a  single  experiment?  This  is  a  matter  of  cal- 
culation, and  the  calculation  must  be  based  upon 
the  ^experience  related  above,  that  the  progres- 
sion in  the  case  of  maize  is  equal  to  two-fifths  of 
the  parental  deviation.  A  cob  with  20  rows 
means  a  deviation  of  7  from  the  average  of  13, 
the  incipient  value  of  my  race.  To  reach  such 
an  average  at  once,  an  ear  would  be  required 
with  7x^/2=17%  rows  above  the  average,  or 
an  ear  with  30-32  rows.  These  never  occur, 
but  the  rule  given  in  a  previous  lecture  gives  a 
method  of  calculating  the  probability  of  their 
occurrence,  or  in  other  words,  the  number  of 
ears  required  to  give  a  chance  of  finding  such 
an  ear.  It  would  take  too  long  to  give  this  cal- 
culation here,  but  I  find  that  approximately  12,- 
000  ears  would  be  required  to  give  one  witli  28 
rows,  which  was  the  highest  number  attained  in 


784 


Fluctuations 


my  experiment,  while  100,000  ears  would  afford 
a  chance  of  one  with  32  rows.*  Had  I  been 
able  to  secure  and  inspect  this  number  of  ears, 
perhaps  I  would  have  needed  only  a  year  to  get 
an  average  of  20  rows.  This  however,  not  be- 
ing the  case,  I  have  worked  for  seven  years,  but 
on  the  other  hand  have  cultivated  all  in  all  only 
about  one  thousand  individuals  for  the  entire 
experiment. 

Obviously  this  reduction  of  the  size  of  the  ex- 
periment is  of  importance.  One  hundred 
thousand  ears  of  corn  could  of  course,  be  se- 
cured directly  from  trade  or  from  some  indus- 
trial culture,  but  corn  is  cultivated  only  to  a 
small  extent  in  Holland,  and  in  most  cases  the 
requisite  number  of  individuals  would  be  larger 
than  that  afforded  by  any  single  plantation. 

Repeated  selection  is  thereby  seen  to  be  the 
means  of  reducing  the  size  of  the  required  cul- 
tures to  possible  measures,  not  only  in  the  ex- 
perimental-garden, but  also  for  industrial  pur- 
poses. A  selection  from  among  60000  - 100000 
individuals  may  be  within  reach  of  Burbank, 
but  of  few  others.  As  a  rule  they  prefer  a 
longer  time  with  a  smaller  lot  of  plants.    This 

*  On  about  200  ears  the  variability  ranges  from  8-22  rows, 
and  this  leads  approximately  to  one  row  more  by  each  doubling 
of  the  numbers  of  instances.  One  ear  with  22  rows  in 
200  would  thus  lead  to  the  expectation  of  one  ear  with  32 
rows   in    100,000   ears. 


Inconstancy  of  Improved  tiacea        785 

is  exactly  what  is  gained  by  repeated  selections. 
To  my  mind  this  reduction  of  the  size  of  the  cul- 
tures is  probably  the  sole  effect  of  the  repeti- 
tion. But  experience  is  lacking  on  this  point, 
and  exact  comparisons  should  be  made  when- 
ever possible,  between  the  descendants  of  a 
unique  but  extreme  choice,  and  a  repeated  but 
smaller  selection.  The  effect  of  the  repetition 
on  the  nourishment  of  the  chosen  representa- 
tives should  be  studied,  for  it  is  clear  that  a 
plant  with  22  rows,  the  parents  and  grandpar- 
ents of  which  had  the  same  number,  indicates  a 
better  condition  of  internal  qualities  than  one 
with  the  same  number  of  rows,  produced  acci- 
dentally from  the  common  race.  In  this  way  it 
may  perhaps  be  possible  to  explain,  why  in  my 
experiment  an  ear  with  22  rows  gave  an  average 
offspring  with  20,  while  the  calculation,  found- 
ed on  the  regression  alone  would  require  a 
parental  ear  with  32  rows. 

However,  as  already  stated,  this  discussion 
is  only  intended  to  convey  some  general  idea 
as  to  the  reduction  of  the  cultures  by  means  of 
repeated  selections,  as  the  material  at  hand  is 
wholly  inadequate  for  any  closer  calculation. 
This  important  point  of  the  reduction  may  be 
illustrated  in  still  another  manner. 

The  sowing  of  very  large  numbers  is  only  re- 
quired because  it  is  impossible  to  tell  from  the 


786  Fluctuations 

inspection  of  the  seeds  which  of  them  will  yield 
the  desired  individual.  But  what  is  impossible 
in  the  inspection  of  the  seeds  may  be  feasible, 
at  least  in  important  measure,  in  the  inspection 
of  the  plants  which  bear  the  seeds.  Whenever 
such  an  inspection  demonstrates  ditferences,  in 
manifest  connection  with  the  quality  under  con- 
sideration, any  one  will  readily  grant  that  it 
would  be  useless  to  sow  the  seeds  of  the  worst 
plants,  and  that  even  the  whole  average  might 
be  thrown  over,  if  it  were  only  possible  to  point 
out  a  number  of  the  best.  But  it  is  clear  that 
by  this  inspection  of  the  parent-plants  the  prin- 
ciple of  repeated  selection  is  introduced  for  two 
succeeding  generations,  and  that  its  application 
to  a  larger  series  of  generations  is  only  a  ques- 
tion of  secondary  importance. 

Summing  up  our  discussion  of  this  first  point 
we  may  assert  that  repeated  selection  is  only 
selection  on  a  small  and  practical  scale,  while  a 
single  choice  would  require  numbers  of  indi- 
viduals higher  than  are  ordinarily  available. 

A  second  discussion  in  connection  with  our 
pedigree-culture  of  corn  is  the  question  whether 
the  amelioration  obtained  was  of  a  dur- 
able nature,  or  only  temporary.  In  other 
words,  whether  the  progeny  of  the  race  would 
remain  constant,  if  cultivated  after  cessation 
of  the  selection.     In  order  to  ascertain  this,  I 


Inconstancy  of  Improved  Races        787 

continued  the  culture  during  several  genera- 
tions, choosing  ears  with  less  than  the  average 
number  of  rows.  The  excellence  of  the 
race  at  once  disappeared,  and  the  ordinary 
average  of  the  variety  from  which  I  had  started 
seven  years  before,  returned  within  two  or  three 
seasons.  This  shows  that  the  attained  improve- 
ment is  neither  fixed  nor  assured  and  is  depend- 
ent on  continued  selection.  This  result  only 
confirms  the  universal  experience  of  breeders, 
which  teaches  the  general  dependency  of  im- 
proved races  on  continued  selection.  Here  a 
striking  contrast  with  elementary  species  or 
true  varieties  is  obvious.  The  strains  which  na- 
ture affords  are  true  to  their  type;  their  aver- 
age condition  remains  the  same  during  all  the 
succeeding  generations,  and  even  if  it  should 
be  slightly  altered  by  changes  in  the  external 
conditions,  it  returns  to  the  type,  as  soon  as 
these  changes  come  to  an  end.  It  is  a  real  aver- 
age, being  the  sum  of  the  contribution  of  all 
the  members  of  the  strain.  Improved  races 
have  only  an  apparent  average,  which  is  in  fact 
biased  by  the  exclusion  of  whole  groups  of  in- 
dividuals. If  left  to  themselves,  their  appear- 
ance changes,  and  the  real  average  soon  re- 
turns. This  is  the  common  experience  of  breed- 
ers. 

A   third   point   is    to    be   discussed    in    con- 


788  Fluctuations 

nection  with  the  detailed  pedigree-cultures.  It 
is  the  question  as  to  what  might  be  expected 
from  a  continuation  of  improvement  selection. 
Would  it  be  possible  to  obtain  any  imaginable 
deviation  from  the  original  type,  and  to  reach 
independency  from  further  selection?  This 
point  has  not  until  now  attracted  any  practical 
interest,  and  from  a  practical  point  of  view  and 
within  the  limits  of  ordinary  cultures,  it  seems 
impossible  to  obtain  a  positive  answer.  But 
in  the  theoretical  discussion  of  the  problems  of 
descent  it  has  become  of  the  highest  unportance, 
and  therefore  requires  a  separate  treatment, 
which  will  be  reserved  for  the  next  lecture. 

Here  we  come  upon  another  equally  diffi- 
cult problem.  It  relates  to  the  proportion  of 
embryonic  or  individual  fluctuation,  to  partial 
variation  as  involved  in  the  process  of  selec- 
tion. Probably  all  qualities  which  may  be  sub- 
jected to  selection  vary  according  to  both  prin- 
ciples, the  embryonic  decision  giving  only  a 
more  definite  average,  around  which  the  parts 
of  the  individual  are  still  allowed  to  oscillate. 
It  is  so  with  the  corn,  and  whenever  two 
or  more  ears  are  ripening  or  even  only  flower- 
ing on  the  same  plant,  differences  of  a  partial 
nature  may  be  seen  in  the  number  of  their  rows. 
These  fluctuations  are  only  small  however,  or- 
dinarily not   exceeding  two   and   rarely   four 


Inconstancy  of  Improved  Races        781) 

rows.  Choosing  always  the  principal  ear, 
the  figures  may  be  taken  to  indicate  the  de- 
gree of  personal  deviation  from  the  average  of 
the  race.  But  whenever  we  make  a  mistake,  and 
perchance  sow  from  an  ear,  the  deviation  of 
which  was  largely  due  to  partial  variation,  the 
regression  should  be  expected  to  become  con- 
siderably larger.  Hence  it  must  be  conceded 
that  exact  calculations  of  the  phenomena  of  in- 
heritance are  subject  to  much  uncertainty, 
resulting  from  our  very  imperfect  knowledge 
concerning  the  real  proportion  of  the  contribut- 
ing factors,  and  the  difficulty  of  ascertaining 
their  influence  in  any  given  case.  Here  also  we 
encounter  more  doubts  than  real  facts,  and  much 
remains  to  be  done  before  exact  calculations 
may  become  of  real  scientific  value. 

Returning  to  the  question  of  the  effects  of  se- 
lection in  the  long  run,  two  essentially  differ- 
ent cases  are  to  be  considered.  Extremes  may 
be  selected  from  among  the  variants  of  ordinary 
fluctuating  variability,  or  from  ever-sporting 
varieties.  These  last  we  have  shown  to  be 
double  races.  Their  peculiar  and  wide  range  of 
variability  is  due  to  the  substitution  of  two 
characters,  which  exclude  one  another,  or  if 
combined,  are  diminished  in  various  degrees. 
Striped  flowers  and  stocks,  "five-leaved"  clover, 
pistilloid   opium-poppies   and  numerous   other 


790  Fluctuations 

monstrosities  have  been  dealt  with  as  instances 
of  such  ever-sporting  varieties. 

Now  the  question  may  be  put,  what  would  be 
the  effect  of  selection  if  in  long  series  of  years 
one  of  the  two  characters  of  such  a  double  race 
were  preferred  continuously,  to  the  complete 
exclusion  of  the  other.  Would  the  race  become 
changed  thereby?  Could  it  be  affected  to  such 
a  degree  as  to  gradually  lose  the  inactive  qual- 
ity, and  cease  to  be  a  double  race? 

Here  manifestly  we  have  a  means  by  which 
to  determine  what  selection  is  able  to  ac- 
complish. Physiologic  experiments  may  be 
said  to  be  too  short  to  give  any  definite 
evidence.  But  cases  may  be  cited  where 
nature  has  selected  during  long  centuries 
and  with  absolute  constancy  in  her  choice. 
Moreover  unconscious  selections  by  man  have 
often  worked  in  an  analogous  manner,  and 
many  cultivated  plants  may  be  put  to  the 
test  concerning  the  evidence  they  might  give 
on  this  point.  Stating  beforehand  the  result  of 
this  inquiry,  we  may  assert  that  long-continued 
selection  has  absolutely  no  appreciable  effect. 
Of  course  I  do  not  deny  the  splendid  results  of 
selection  during  the  first  few  years,  nor  the  ne- 
cessity of  continued  selection  to  keep  the  im- 
proved races  to  the  height  of  their  ameliorated 
qualities.     I  only  wish  to  state  that  the  work 


Inconstancy  of  Improved  Races        71)1 

of  selection  here  finds  its  limit  and  that  cen- 
turies and  perhaps  geologic  periods  of  contin- 
ued effort  in  the  same  direction  are  not  capable 
of  adding  anything  more  to  the  initial  effect. 
Some   illustrative   examples   may   suffice   to 
prove  the  validity  of  this  assertion.    Every  bot- 
anist who  has  studied  the  agricultural  practice 
of  plant-breeding,  or  the  causes  of  the  geo- 
graphic distribution  of  plants,  will  easily  recall 
to  his  mind  numerous  similar  cases.    Perhaps 
the  most  striking  instance  is  afforded  by  culti- 
vated biennial  plants.    The  most  important  of 
them  are  forage-beets  and  sugar-beets.     They 
are,   of  course,   cultivated   only  as   biennials, 
but  some  annual  specimens  may  be  seen  each 
year  and   in  nearly  every  field.     They   arise 
from  the  same  seed  as  the  normal  individuals, 
and  their  number  is  obviously  dependent  on 
external  conditions,  and  especially  on  the  time 
of  sowing.     Ordinary  cultures  often  show  as 
much  as  1^  of  these  useless  plants,  but  the  exi- 
gencies of  time  and  available  labor  often  com- 
pel the  cultivator  to  have  a  large  part  of  his 
fields    sown   before    spring.      In    central    Eu- 
rope, where  the  climate  is  unfavorable  at  this 
season,  the  beets  respond  by  the  production  of 
far  larger   proportions   of  annual   specimens, 
their  number  coming  often  up  to  20^  or  more, 
thus  constituting  noticeable  losses  in  the  prod- 


792  Fluctuations 

uct  of  the  whole  field.  Rimpau,  who  has  made 
a  thorough  study  of  this  evil  and  has  shown  its 
dependency  on  various  external  conditions,  has 
also  tried  to  find  methods  of  selection  with  the 
aim  of  overcoming  it,  or  at  least  of  reducing  it 
to  uninjurious  proportions.  But  in  these  ef- 
forts he  has  reached  no  practical  result.  The 
annuals  are  simply  inexterminable. 

Coming  to  the  alternative  side  of  the  problem 
it  is  clear  that  annuals  have  always  been  ex- 
cluded in  the  selection.  Their  seeds  cannot  be 
mixed  with  the  good  harvest,  not  even  accident- 
ally, since  they  have  ripened  in  a  previous  year. 
In  order  to  bear  seeds  in  the  second  year  beets 
must  be  taken  from  the  field,  and  kept  free 
from  frost  through  the  winter.  The  following 
spring  they  are  planted  out,  and  it  is  obvious 
that  even  the  most  careless  farmer  is  not  liable 
to  mix  them  with  annual  specimens.  Hence  we 
may  conclude  that  a  strict  and  unexcelled  proc- 
ess of  selection  has  been  applied  to  the  destruc- 
tion of  this  tendency,  not  only  for  sugar-beets, 
since  Vilmorin's  time,  when  selection  had  be- 
come a  well  understood  process,  but  also  for 
forage-beets  since  the  beginning  of  beet- 
culture.  Although  unconscious,  the  selection  of 
biennials  must  have  been  uninterrupted  and 
strict  throughout  many  centuries. 

It  has  had  no  effect  at  all.    Annuals  are  seen 


Inconstancy  of  Improved  Races        793 

to  return  every  year.  They  are  ineradicable. 
Every  individual  is  in  the  possession  of  this 
latent  quality  and  liable  to  convert  it  into 
activity  as  soon  as  the  circumstances  provoke 
its  appearance,  as  proved  by  the  increase  of  an- 
nuals in  the  early  sowings.  Hence  the  conclu- 
sion that  selection  in  the  long  run  is  not  ade- 
quate to  deliver  plants  from  injurious  qualities. 
Other  proofs  could  be  given  by  other  biennials, 
and  among  them  the  stray  annual  plants  of 
common  carrots  are  perhaps  the  most  noto- 
rious. In  my  own  cultures  of  evening-prim- 
roses I  have  preferred  the  annuals  and  ex- 
cluded the  biennials,  but  without  being  able  to 
produce  a  pure  annual  race.  As  soon  as  cir- 
cumstances are  favorable,  the  biennials  return 
in  large  numbers.  Cereals  give  analogous 
proofs.  .  Summer  and  winter  varieties  have 
been  cultivated  separately  for  centuries,  but  in 
trials  it  is  often  easy  to  convert  the  one  into 
the  other.  No  real  and  definite  isolation  has 
resulted  from  the  effect  of  the  long  continued 
unconscious  selection. 

Striped  flowers,  striped  fruits,  and  especially 
striped  radishes  afford  further  examples.  It 
would  be  quite  superfluous  to  dwell  upon  them. 
Selection  always  tends  to  exclude  the  mono- 
chromatic specimens,  but  does  not  proven t 
their  return  in  every  generation.      Numorous 


794  Fluctuations 

rare  monstrosities  are  in  the  same  category, 
especially  when  they  are  of  so  rare  occurrence 
as  not  to  give  any  noticeable  contribution  to 
the  seed-production,  or  even  if  they  render  their 
bearers  incapable  of  reproduction.  In  such 
cases  the  selection  of  normal  plants  is  very  se- 
vere or  even  absolute,  but  the  anomalies  are  by 
no  means  exterminated.  Any  favorable  circum- 
stances, or  experimental  selection  in  their  be- 
half shows  them  to  be  still  capable  of  full  devel- 
opment. Numerous  cases  of  such  subordinate 
hereditary  characters  constitute  the  greater 
part  of  the  science  of  vegetable  teratology. 

If  it  should  be  objected  that  all  these  cases 
cover  too  short  a  time  to  be  decisive,  or  at  least 
fail  in  giving  evidence  relative  to  former  times, 
alpine  plants  afford  a  proof  which  one  can 
hardly  expect  to  be  surpassed.  During  the 
whole  present  geologic  epoch  they  have  been 
subjected  to  the  never  failing  selection  of  their 
climate  and  other  external  conditions.  They 
exhibit  a  full  and  striking  adaptation  to  these 
conditions,  but  also  possess  the  latent  capacity 
for  assuming  lowland  characters  as  soon  as 
they  are  transported  into  such  environment. 
Obviously  this  capacity  never  becomes  active 
on  the  mountains,  and  is  always  counteracted 
by  selection.  This  agency  is  evidently  without 
any  effect,  for  as  we  have  seen  when  dealing 


Inconstancy  of  Improved  Races       7ii5 

with  the  experiments  of  Nageli,  Bonnier  and 
others,  each  single  individual  may  change  its 
habits  and  its  aspect  in  response  to  transplanta- 
tion. The  climate  has  an  exceedingly  great  in- 
fluence on  each  individual,  but  the  continuance 
of  this  influence  is  without  permanent  result. 

So  much  concerning  ever-sporting  varie- 
ties and  double  adaptations.  We  now  come  to 
the  effects  of  a  continuous  selection  of  simple 
characters. 

Here  the  sugar-beets  stand  preeminent. 
Since  Vilmorin's  time  they  have  been  selected 
according  to  the  amount  of  sugar  in  their  roots, 
and  the  result  has  been  the  most  striking  that 
has  ever  been  attained,  if  considered  from  the 
standpoint  of  practice.  But  if  critically  exam- 
ined, with  no  other  aim  than  a  scientific  appre- 
ciation of  the  improvement  in  comparison  with 
other  processes  of  selection,  the  support  of  the 
evidence  for  the  theory  of  accumulative  influ- 
ence proves  to  be  very  small. 

The  amount  of  sugar  is  expressed  by  percent- 
age-figures. These  however,  are  dependent  on 
various  causes,  besides  the  real  quantity  of  su- 
gar produced.  One  of  these  causes  is  the  quan- 
tity of  watery  fluid  in  the  tissues,  and  this  in  its 
turn  is  dependent  on  the  culture  in  diyer  or 
moister  soil,  and  on  the  amount  of  moisture  in 
the  air,  and  the  same  variety  of  sugar-beets 


796  Fluctuations 

yields  higher  percentage-figures  in  a  dry  region 
than  in  a  wet  one.  This  is  seen  when  compar- 
ing, for  instance,  the  results  of  the  analyses 
from  the  sandy  provinces  of  Holland  with  those 
from  the  clay-meadows,  and  it  is  very  well 
known  that  Californian  beets  average  as  high 
as  26^  or  more,  while  the  best  European  beets 
remain  at  about  20^.  As  far  as  I  have  been 
able  to  ascertain,  these  figures  however,  are  not 
indicative  of  any  difference  of  race,  but  simply 
direct  responses  to  the  conditions  of  climate 
and  of  soil. 

Apart  from  these  considerations  the  improve- 
ment reached  in  half  a  century  or  in  about 
twenty  to  thirty  generations  is  not  suggestive 
of  anything  absolute.  Everything  is  fluctuating 
now,  even  as  it  was  at  the  outset,  and  equally 
dependent  on  continual  care.  Vilmorin  has 
given  some  figures  for  the  beets  of  the  first 
generations  from  which  he  started  his  race.  He 
quotes  14^  as  a  recommendable  amount,  and  7 
and  21  as  the  extreme  instances  of  his  analy- 
ses. However  incorrect  these  figures  may  be, 
they  coincide  to  a  striking  degree  with  the  pres- 
ent condition  of  the  best  European  races.  Of 
course  minor  values  are  excluded  each  year  by 
the  selection,  and  in  consequence  the  average 
value  has  increased.  For  the  year  1874  we  find 
a  standard  of  10  - 14^  considered  as  normal, 


Inconstancy  of  Improved  Races        797 

bad  years  giving  10;^,  good  years  from  Vl'j^  to 
14;^  in  the  average.  Extreme  instances  exceeded 
17^.     From  that  time  the  practice  of  the  pohir- 
ization  of  the  juice  for  the  estimate  of  the  sugar 
has  rapidly  spread  throughout  Europe,  and  a 
definite  increase  of  the  average  value  soon  re- 
sulted.    This  however,  often  does  not  exceed 
14^,  and  beets  selected  in  the  field  for  the  pur- 
pose of  polarization  come  up  to  an  average  of 
15  to  16^,  varying  downward  to  less  than  10^ 
and  upward  to  20  and  21^.     In  the  main  the  fig- 
ures are  the  same  as  those  of  Vilmorin,  the 
range  of  variability  has  not  been  reduced,  and 
higher  extremes  are  not  reached.     An  average 
increase  of  1^  is  of  great  practical  importance, 
and  nothing  can  excel  the  industry  and  care  dis- 
played in  the  improvement  of  the  beet-races. 
Notwithstanding  this  a  lasting  influence  has  not 
been  exercised;  the  methods  of  selection  have 
been  improved,  and  the  number  of  polarized 
beets  has  been  brought  up  to  some  hundreds  of 
thousands  in  single  factories,  but  the  improve- 
ment is  still  as  dependent  upon  continuous  selec- 
tion as  it  was  half  a  century  ago. 

The  process  is  practically  very  successful,  but 
the  support  afforded  by.it  to  the  selection- 
theory  vanishes  on  critical  examination. 


Lecture  XXVIII 

ARTIFICIAL  AND   NATURAL  SELECTION 

The  comparison  of  artificial  and  natural  se- 
lection has  furnished  material  support  for  the 
theory  of  descent,  and  in  turn  been  the  object 
of  constant  criticism  since  the  time  of  Darwin. 
The  criticisms,  in  greater  part,  have  arisen 
chiefly  from  an  imperfect  knowledge  of  both 
processes.  By  the  aid  of  distinctions  recently 
made  possible,  the  contrast  between  elementary 
species  and  improved  races  has  become  much 
more  vivid,  and  promises  to  yield  better  results 
on  which  to  base  comparisons  of  artificial  and 
natural  selection. 

Elementary  species,  as  we  have  seen  in 
earlier  lectures,  occur  in  wild  and  in  culti- 
vated plants.  In  older  genera  and  systematic 
species  they  are  often  present  in  small  numbers 
only,  but  many  of  the  more  recent  wild  types 
and  also  many  of  the  cultivated  forms 
are  very  rich  in  this  respect.  In  agriculture 
the  choice  of  the  most  adequate  elementary 
forms     for     any     special     purpose     is     ac- 

798 


Artificial  and  Natural  Selection        799 

knowledged  as  the  first  step  in  the  way 
of  selection,  and  is  designated  by  the  name 
of  variety-testing,  applying  the  term  variety  to 
all  the  subdivisions  of  systematic  species  indis- 
criminately. In  natural  processes  it  bears  tlie 
title  of  survival  of  species.  The  fact  that  re- 
cent types  show  large  numbers,  and  in  some  in- 
stances even  hundreds  of  minor  constant  fonus, 
while  the  older  genera  are  considerably  reduced 
in  this  respect,  is  commonly  explained  by  the 
assumption  of  extinction  of  species  on  a  corre- 
spondingly large  scale.  This  extinction  is  con- 
sidered to  affect  the  unfit  in  a  higher  measure 
than  the  fit.  Consequently  the  former  vanish, 
often  without  leaving  any  trace  of  their  exist- 
ence, and  only  those  that  prove  to  be  sufficiently 
adapted  to  the  surrounding  external  conditions, 
resist  and  survive. 

This  selection  exhibits  far-reaching  analo- 
gies between  the  artificial  and  the  natural  proc- 
esses, and  is  in  both  cases  of  the  very  highest 
importance.  In  nature  the  dying  out  of  unfit 
mutations  is  the  result  of  the  great  struggle  for 
life.  In  a  previous  lecture  we  have  compared 
its  agency  with  that  of  a  sieve.  All  elements 
which  are  too  small  or  too  weak  fall  through, 
and  only  those  are  preserved  which  resist  the 
sifting  process.  Reduced  in  number  they 
thrive  and  multiply  and   are  thus  enabh^l   to 


800  Fluctuations 

strike  out  new  mutative  changes.  These  are 
again  submitted  to  the  sifting  tests,  and  the  fre- 
quent repetition  of  this  process  is  considered 
to  give  a  good  explanation  of  the  manifold, 
highly  complicated,  and  admirable  structures 
which  strike  the  beginner  as  the  only  real  adap- 
tations in  nature. 

Exactly  in  the  same  way  artificial  selection 
isolates  and  preserves  some  elementary  species, 
while  it  destroys  others.  Of  course  the  time  is 
not  sufficient  to  secure  new  mutations,  or  at 
least  these  are  only  rare  at  present,  and 
their  occurrence  is  doubtful  in  historic  periods. 
Apart  from  this  unavoidable  difference  the 
analog}^  between  natural  and  artificial  selection 
appears  to  me  to  be  very  striking. 

This  form  of  selection  may  be  termed  selec- 
tion between  species.  Opposed  to  it  stands  the 
selection  within  the  elementary  species  or  va- 
riety. It  has  of  late,  alone  come  to  be  known  as 
selection,  though  in  reality  it  does  not  deserve 
this  distinction.  I  have  already  detailed  the 
historical  evidence  which  gives  preference  to 
selection  between  species.  The  process  can  best 
be  designated  by  the  name  of  intra-specific  se- 
lection, if  it  is  understood  that  the  term  intra- 
specific  is  meant  to  apply  to  the  conception  of 
small  or  elementary  species. 

I  do  not  wish  to  propose  new  terms,   but 


Artificial  and  Natural  Selection        801 

I  think  that  the  principal  differences  might  bet- 
ter become  understood  by  the  introduction  of 
the  word  election  into  the  discussion  of  (lues- 
tions  of  heredity.  Election  meant  formerly  the 
preferential  choice  of  single  individuals,  wliilo 
the  derivation  of  the  word  selection  points  to  a 
segregation  of  assemblies  into  their  hirger  parts. 
Or  to  state  it  in  a  shorter  way,  individual  selec- 
tion is  exactly  what  is  usually  termed  elec- 
tion. Choosing  one  man  from  among  thou- 
sands is  to  elect  him,  but  a  select  party  is  a 
group  of  chosen  persons.  There  would  be  no 
great  difficulty  in  the  introduction  of  the  word 
election,  as  breeders  are  already  in  the 
habit  of  calling  their  choice  individuals  ^'  elite," 
at  least  in  the  case  of  beets  and  of  cereals. 

This  intra-specific  selection  affords  a  second 
point  for  the  comparison  between  natural  and 
artificial  processes.  This  case  is  readily  grant- 
ed to  be  more  difficult  than  the  first,  but  there 
can  be  no  doubt  that  the  similaritv  is  due  to 
strictly  comparable  causes.  In  practice  this 
process  is  scarcely  second  in  importance  to  the 
selection  between  species,  and  in  numerous 
cases  it  rests  upon  it,  and  crowns  it,  bringing 
the  isolated  forms  up  to  their  highest  ])()ssiblo 
degree  of  usefulness.  In  nature  it  does  quite 
the  same,  adapting  strains  of  individuals  to 
the  local  conditions  of  their  environment.    Tm- 


802  Fluctuations 

proved  races  do  not  generally  last  very  long 
in  practice;  sooner  or  later  tliey  are  surpassed 
by  new  selections.  Exactly  so  we  may  imagine 
the  agency  of  natural  intra-specific  selection. 
It  produces  the  local  races,  the  marks  of  which 
disappear  as  soon  as  the  special  external  con- 
ditions cease  to  act.  It  is  responsible  only  for 
the  smallest  lateral  branches  of  the  pedigree, 
but  has  nothing  in  common  with  the  evolution 
on  the  main  stems.  It  is  of  very  subordinate 
importance. 

These  assertions  of  course,  are  directly  op- 
posed to  the  current  run  of  scientific  belief,  but 
they  are  supported  by  facts.  A  considerable 
part  of  the  evidence  has  already  been  dealt 
with  and  for  our  closing  discussion  only  an  ex- 
act comparison  remains  to  be  made  between  the 
two  detailed  types  of  intra-specific  selection.  In 
coming  to  this  I  will  first  dwell  upon  some  in- 
termediate types  and  conclude  with  a  critical 
discussion  of  the  features  of  artificial  selection, 
which  to  my  mind  prove  the  invalidity  of  the 
conclusions  drawn  from  it  in  behalf  of  an  ex- 
planation of  the  processes  of  nature. 

Natural  selection  occurs  not  only  in  the  wild 
state,  but  is  also  active  in  cultivated  fields. 
Here  it  regulates  the  struggle  of  the  selected 
varieties  and  improved  races  with  the  older 
types,  and  even  with  the  wild  species.    In  a  pre- 


Artificial  and  Natural  Selection        803 

vious  lecture  I  have  detailed  the  rapid  increase 
of  the  wild-oats  in  certain  years,  and  described 
the  experiments  of  Risler  and  Rimpau  in  the 
running  out  of  select  varieties.  The  agency  is 
always  the  same.  The  preferred  forms,  wliir-h 
give  a  larger  harvest,  are  generally  more 
sensitive  to  injurious  influences,  more  dependent 
on  rich  manure  and  on  adequate  treatment. 
The  native  varieties  have  therefore  the  advan- 
tage, when  climatic  or  cultural  conditions  are 
unfavorable  for  the  fields  at  large.  They  suf- 
fer in  a  minor  degree,  and  are  thereby  enabled 
to  propagate  themselves  afterwards  more  rap- 
idly and  to  defeat  the  finer  types.  This 
struggle  for  life  is  a  constant  one,  and  can 
easily  be  followed,  whenever  the  composition 
of  a  strain  is  noted  in  successive  years.  It  is 
well  appreciated  by  breeders  and  farmers,  be- 
cause it  is  always  liable  to  counteract  their 
endeavors  and  to  claim  their  utmost  efforts  to 
keep  their  races  pure.  There  can  be  no  doubt 
that  exactly  the  same  struggle  exempt  from 
man's  intrusion  is  fought  out  in  the  wild  stato. 
Local  races  of  wild  plants  have  not  been 
the  object  for  field-observations  recently.  Some 
facts  however,  are  known  concerning  them.  On 
the  East  Friesian  Islands  in  the  North  Sea  the 
flowers  are  strikingly  larger  and  brighter  col- 
ored than  those  of  the  same  species  on  the 


804  Fluctuations 

neighboring  continent.  This  local  difference  is 
ascribed  by  Behrens  to  a  more  severe  selection 
by  the  pollinating  insects  in  consequence  of  their 
lesser  frequency  on  these  very  windy  isles. 
Seeds  of  the  pines  from  the  Himalayas  yield 
cold-resisting  young  plants  if  gathered  from 
trees  in  a  high  altitude,  while  the  seeds  of  the 
same  species  from  lower  regions  yield  more 
sensitive  seedlings.  Similar  instances  are  af- 
forded by  Rhododendron  and  other  mountain 
species.  According  to  Cieslar  corresponding 
differences  are  shown  by  seeds  of  firs  and 
larches  from  alpine  and  lowland  provinces. 

Such  changes  are  directly  dependent  on  ex- 
ternal influences.  This  is  especially  manifest 
in  experiments  extending  the  cultures  in  higher 
or  in  more  northern  regions.  The  shorter 
summer  is  a  natural  agent  of  selection;  it  ex- 
cludes all  individuals  which  cannot  ripen  their 
seeds  during  so  short  a  period.  Only  the  short- 
lived ones  survive.  Schiibeler  made  very  strik- 
ing experiments  with  corn  and  other  different 
cereals,  and  has  succeeded  in  making  their  cul- 
ture possible  in  regions  of  Norway  where  it  for- 
merly failed.  In  the  district  of  Christiania,  corn 
had  within  some  few  years  reduced  its  lifetime 
from  123  to  90  days,  yielding  smaller  stems  and 
fewer  kernels,  but  still  sufficient  to  make  its 
culture  profitable  under  the  existing  conditions. 


Artificial  and  Natural  Selection        8(J5 

This  change  was  not  permanent,  but  was  ob- 
served to  diminish  rapidly  and  to  disappear 
entirely,  whenever  the  Norwegian  strain  was 
cultivated  in  the  southern  part  of  Germany.  It 
was  a  typical  improved  race,  dependent  on  con- 
tinual selection  by  the  short  summers  which  liad 
produced  it.  Similar  results  have  been  reached 
by  Von  Wettstein  in  the  comparison  of  kinds 
of  flax  from  different  countries.  The  analogy 
between  such  cultivated  local  races  and  the  lo- 
cal races  of  nature  is  quite  striking.  The  prac- 
tice of  seed-exchange  rests  for  a  large  part  on 
the  experience  that  the  characters,  acquired  un- 
der the  definite  climatic  and  cultural  conditions 
of  some  select  regions,  hold  good  for  one  or  two, 
and  sometimes  even  more  generations,  before 
they  decrease  to  practical  uselessness.  The 
Probstei,  the  Hanna  and  other  districts  owe 
their  wealth  to  this  temporary  superiority  of 
their  wheat  and  other  cereals. 

Leaving  these  intermediate  forms  of  selec- 
tion, we  now  come  to  our  principal  point.  It 
has  already  been  discussed  at  some  length  in  the 
previous  lecture,  but  needs  further  consider- 
ation. It  is  the  question  whether  intra-specifi<' 
selection  may  be  regarded  as  a  cause  of  last- 
ing and  ever-increasing  improvement.  Tiiis 
is  assumed  by  biologists  who  consider  fluc- 
tuating variability  as  the  main  source  of  ]iro- 


806  Fluctuations 

gression  in  the  organic  world.  But  the  ex- 
perience of  the  breeders  does  not  support  this 
view,  since  the  results  of  practice  prove  that 
selection  according  to  a  constant  standard 
soon  reaches  a  limit  which  it  is  not  capable 
of  transgressing.  In  order  to  attain  further 
improvements  the  method  of  selection  itself 
must  be  improved.  A  better  and  sharper 
method  assures  the  choice  of  more  valuable 
representatives  of  the  race,  even  if  these  must 
be  sought  for  in  far  larger  numbers  of  in- 
dividuals, as  is  indicated  by  the  law  of  Quetelet. 

Continuous  or  even  prolonged  improvement 
of  a  cultivated  race  is  not  the  result  of  frequent- 
ly repeated  selection,  but  of  the  improvement  of 
the  standard  of  appreciation.  Nature,  as  far  as 
we  know,  changes  her  standard  from  time  to 
time  only  in  consequence  of  the  migrations  of 
the  species,  or  of  local  changes  of  climate. 
Afterwards  the  new  standard  remains  un- 
changed for  centuries. 

Selection,  according  to  a  constant  standard, 
reaches  its  results  in  few  generations.  The 
experience  of  Van  Mons  and  other  breeders  of 
apples  shows  that  the  limit  of  size  and  luscious- 
ness  may  be  soon  attained.  Vilmorin's  ex- 
periments with  wild  carrots  and  those  of  Car- 
riere  with  radishes  lead  to  the  same  conclusion 
as  regards  roots.     Improvements  of  flowers  in 


Artificial  and  Natural  Sdection        807 

size  and  color  are  usually  easy  and  rapid  in  the 
beginning,  but  an  impassable  limit  is  soon 
reached.  Numerous  other  instances  could  be 
given. 

Contrasted  with  these  simple  cases  is  the 
method  of  selecting  sugar-beets.  More  than 
once  I  have  alluded  to  this  splendid  exam- 
ple of  the  influence  of  man  upon  domestic  races, 
and  tried  to  point  out  how  little  support  it  af- 
fords to  the  current  scientific  opinion  concern- 
ing the  power  of  natural  selection.  For  this 
reason  it  is  interesting  to  see  how  a  gradual 
development  of  the  methods  of  selection  has 
been,  from  the  very  outset,  one  of  the  chief  aims 
of  the  breeders.  None  of  them  doubts  that  an 
improvement  of  the  method  alone  is  adequate  to 
obtain  results.  This  result,  in  the  main,  is  the 
securing  of  a  few  per-cent  more  of  sugar,  a 
change  hardly  comparable  with  that  progress 
in  evolution,  which  our  theories  are  destined  to 
explain. 

Vilmorin's  original  method  was  a  very  sini])le 
one.  Polarization  was  still  undiscovered  in  his 
time.  He  determined  the  specific  weight  of  his 
beets,  either  by  weighing  them  as  a  whole,  or  by 
using  a  piece  cut  from  the  base  of  the  roots  and 
deprived  of  its  bark,  in  order  to  test  only  the 
sugar-tissues.  The  pieces  were  floated  in  solu- 
tions of  salt,  which  were  diluted  until  the  pieces 


808  Fluctuations 

began  to  sink.  Their  specific  weight  at  that  mo- 
ment was  determined  and  considered  to  be  a 
measure  of  the  corresponding  value  of  the  beet. 
This  principle  was  afterwards  improved  in  two 
ways.  The  first  was  a  selection  after  the  salt- 
solution-method,  but  performed  on  a  large  scale. 
After  some  few  determinations,  a  solution  was 
made  of  such  strength  as  to  allow  the  greater 
number  of  the  beets  to  float,  and  only  the  best 
to  sink  down.  In  large  vessels  thousands  of 
beets  could  be  tested  in  this  way,  to  select  a 
few  of  the  very  heaviest.  The  other  improve- 
ment was  the  determination  of  the  specific 
weight  of  the  sap,  pressed  out  from  the  tis- 
sue. It  was  more  tedious  and  more  expensive, 
but  more  direct,  as  the  influence  of  the  air- 
cavities  of  the  tissue  was  excluded.  It  pre- 
pared the  way  for  polarization. 

This  was  introduced  about  the  year  1874  in 
Germany,  and  soon  became  generally  accepted. 
It  allowed  the  amount  of  sugar  to  be  measured 
directly,  and  with  but  slight  trouble.  Thou- 
sands of  beets  could  be  tested  yearly  by  this 
method,  and  the  best  selected  for  the  production 
of  seed.  In  some  factories  a  standard  percent- 
age is  determined  by  previous  inquiries,  and  the 
mass  of  the  beets  is  tested  only  by  it.  In  others 
the  methods  of  taking  samples  and  clearing  the 
sap  have  been  improved  so  far  as  to  allow  the 


Artificial  and  Natuial  ISdcctiuu        m\) 

exact  determination  of  three  hundred  Ihuuband 
polarization-values  of  beets  within  a  few  weeks. 
Such  figures  give  the  richest  material  for  statis- 
tical studies,  and  at  once  indicate  the  best  roots, 
while  they  enable  the  breeder  to  change  his 
standard  in  accordance  with  the  results  at  an\- 
time.  Furthermore  they  allow  the  mass  of 
the  beets  to  be  divided  into  groups  of  dif- 
ferent quality,  and  to  produce,  besides  the 
seeds  for  the  continuation  of  the  race,  a  iirst- 
class  and  second-class  product  and  so  on.  lu 
the  factory  of  Messrs.  Kuhn  &  Co.,  at  Xaarden, 
Holland,  the  grinding  machine  has  been  mark- 
edly improved,  so  as  to  tear  all  cell-walls  asun- 
der, open  all  cells,  and  secure  the  whole  of  the 
sap  within  less  than  a  minute,  and  without  heat- 
ing. 

It  would  take  too  long  to  go  into  further  de- 
tails, or  to  describe  the  simultaneous  changes 
that  have  been  applied  to  the  culture  of  the 
elite  strains.  The  detailed  features  suffice 
to  show  that  the  chief  care  of  the  breeder  in  this 
case  is  a  continuous  amelioration  of  tlie  method 
of  selecting.  It  is  manifest  that  the  ])rogres- 
sion  of  the  race  is  in  the  main  due  to  great  tech- 
nical improvements,  and  not  solely  to  the  repe- 
tition of  the  selection. 

Similar  facts  may  be  seen  on  all  the  great 
lines  of  industrial  selection.     An  increasing  ap- 


810  Fluatuations 

preciation  of  all  the  qualities  of  the  selected 
plants  is  the  common  feature.  Morphological 
characters,  and  the  capacity  of  yielding  the 
desired  products,  are  the  first  points  that 
strike  the  breeder.  The  relation  to  climate  and 
the  dependence  on  manure  soon  follow,  but  the 
physiological  and  chemical  sides  of  the  problem 
are  usually  slow  of  recognition  in  the  methods 
of  selection.  When  visiting  Mr.  de  Vilmorin  at 
Paris  some  years  ago,  I  inspected  his  laboratory 
for  the  selection  of  potatoes.  In  the  method  in 
use,  the  tubers  were  rubbed  to  pulp  and  the 
starch  was  extracted  and  measured.  A  starch- 
percentage  figure  was  determined  for  each 
plant,  and  the  selection  of  the  tubers  for  plant- 
ing was  founded  upon  this  result.  In  the  same* 
way  wheat  has  been  selected  by  Dippe  at 
Quedlinburg,  first  by  a  determination  of  its 
nitrogenous  contents  in  general,  and  secondly 
by  the  amount  of  the  substances  which  deter- 
mine its  value  for  baking  purposes. 

The  celebrated  rye  of  Schlanstedt  was  pro- 
duced by  the  late  Mr.  Himpau  in  a  similar  man- 
ner and  was  put  on  the  market  between  1880  and 
1890  and  was  received  with  great  favor  through- 
out central  Europe,  especially  in  Germany  and 
in  France.  It  is  a  tall  variety,  with  vigorous 
stems  and  very  long  heads,  the  kernels  of 
which  are  nearlv  double  the  size  of  those  of  the 


Artificial  and  Natural  Selection        bii 

ordinary  rye,  and  are  seen  protruding,  wiiou 
ripe,  from  between  the  scales  of  the  spikelets. 
It  is  unfit  for  poor  soils,  but  is  one  of  the  very 
best  varieties  for  soils  of  medium  fertility    in 
a  temperate  climate.    It  is  equal  in  the  produc- 
tion  of   grain  to   the   best   French    sorts,   but 
far  surpassing  them  in  its  amount  of  straw. 
It  was  perfected  at  the  farm  of  SchlanstcMlt 
very  slowly,  according  to  the  current  concep- 
tions   of    the    period.      The    experiment    was 
started  in  the  year  1866,  at  which  time  Kini- 
pau  collected  the  most  beautiful   heads   from 
among     his     fields,     and     sowed     their     ker- 
nels in  his  experiment-garden.     From  this  first 
culture  the  whole  race  was  derived.    Every  year 
the  best  ears  of  the  strain  were  chosen  for  re- 
peated culture,  under  experimental  care,  while 
the  remainder  was  multiplied  in  a  field  to  fur- 
nish the  seeds  for  large  and  continually  increas- 
ing areas  of  his  farms. 

Two  or  three  years  were  required  to  pro- 
duce the  quantity  of  seed  of  each  kind  reiiuired 
for  all  the  fields  of  Schlanstedt.  The  exi)ori- 
ment-garden,  which  through  the  kindness  of  M  r. 
Rimpau  I  had  the  good  fortune  of  visiting  more 
than  once  between  1875  and  1878,  was  situ- 
ated in  the  middle  of  his  fann,  at  some  dis- 
tance from  the  dwellings.  Of  course  it  was 
treated  with  more   care,   and   especially   kept 


812  Fluctuations 

in  better  conditions  of  fertility  than  was 
possible  for  the  fields  at  large.  A  con- 
tinued study  of  the  qualities  and  exigencies  of 
the  elite  plants  accompanied  this  selection, 
and  gave  the  means  of  gradually  increasing  the 
standard.  Eesistance  against  disease  was  ob- 
served and  other  qualities  were  ameliorated  in 
the  same  manner.  Mr.  Eimpau  repeatedly  told 
me  that  he  was  most  anxious  not  to  overlook  any 
single  character,  because  he  feared  that  if  any 
of  them  might  become  selected  in  the  wrong 
way,  perchance  unconsciously,  the  whole  strain 
might  suffer  to  such  a  degree  as  to  make  all  the 
other  ameliorations  quite  useless.  With  this 
purpose  the  number  of  plants  per  acre  was 
kept  nearly  the  same  as  those  in  the  fields, 
and  the  size  of  the  culture  was  large  enough 
every  year  to  include  the  best  kernels  of  quite  a 
number  of  heads.  These  were  never  separated, 
and  exact  individual  pedigrees  were  not  in- 
cluded in  the  plan.  This  mixture  seemed  to 
have  the  advantage  of  keeping  up  an  average 
value  of  the  larger  number  of  the  characters, 
which  either  from  their  nature  or  from  their 
apparent  unimportance  had  necessarily  to  be 
neglected. 

After  ten  years  of  continuous  labor,  the  rye 
of  Eimpau  caught  the  attention  of  his  neigh- 
bors, being  manifestly  better  than  that  of  ordi- 


Artificial  and  Natural  Selection        813 

nary  sowings.  Originally  he  bad  made  liis  eul 
tures  for  the  improvement  of  his  own  fields  only. 
Gradually  however,  he  began  to  sell  his  product 
as  seed  to  others,  though  he  found  the  dilTereuce 
still  very  slight.  After  ten  years  more,  about 
1886,  he  was  able  to  sell  all  his  rye  as  see<l 
thereby  making  of  course  large  profits.  It  is 
now  acknowledged  as  one  of  the  best  sorts, 
though  in  his  last  letter  Mr.  Eimpau  announced 
to  me  that  the  profits  began  to  decline  as  other 
selected  varieties  of  rye  became  known.  The 
limit  of  productiveness  was  reached,  and  to  sur- 
mount this,  selection  had  to  be  begun  again 
from  some  new  and  better  starting  point. 

This  new  starting  point  invokes  quite  another 
principle  of  selection,  a  principle  which  threat- 
ens to  make  the  contrast  between  artificial  and 
natural  selection  still  greater.  In  fact  it  is  noth- 
ing new,  being  in  use  formerly  in  the  selection 
of  domestic  animals,  and  having  been  api)liod 
by  Vilmorin  to  his  sugar-beets  more  than  half  a 
century  ago.  Why  it  should  ever  have  bom 
overlooked  and  neglected  in  the  selection  of 
sugar-beets  now  is  not  clear. 

The  principle  in  itself  is  very  simple.  It 
agrees  that  the  visible  characters  of  au  animal 
or  a  plant  are  only  an  imperfect  measure  foi'  its 
hereditary  qualities,  instead  of  being  the  real 
criterion  to  be  relied  upon,  as  is  the  current  be- 


814      •  Fluctuations 

lief.  It  further  reasons  that  a  direct  apprecia- 
tion of  the  capacity  of  inheritance  can  only  be 
derived  from  the  observation  of  the  inheritance 
itself.  Hence  it  concludes  that  the  average 
value  of  the  offspring  is  the  only  real  standard 
by  which  to  judge  the  representatives  of  a  race 
and  to  found  selection  upon. 

These  statements  are  so  directly  opposed  to 
views  prevalent  among  plant-breeders,  that  it 
seems  necessary  to  deal  with  them  from  the 
theoretical  and  experimental,  as  well  as  from 
the  practical  side. 

The  theoretical  arguments  rest  on  the  divi- 
sion of  the  fluctuating  variability  into  the  two 
large  classes  of  individual  or  embryonic,  and  of 
partial  deviations.  We  have  dealt  with  this  di- 
vision at  some  length  in  the  previous  lecture. 
It  will  be  apparent  at  once,  if  we  choose  a  defi- 
nite example.  Let  us  ask  what  is  the  real  sig- 
nificance of  the  percentage-figure  of  a  single 
plant  in  sugar-beets.  This  value  depends  in 
the  first  place,  on  the  strain  or  family  from 
which  the  beet  has  been  derived,  but  this  pri- 
mary point  may  be  neglected  here,  because  it 
is  the  same  for  all  the  beets  of  any  lot,  and  de- 
termines the  average,  around  which  all  are  fluc- 
tuating. 

The  deviation  of  the  percentage-figure  of  a 
single  beet  depends  on  two  main  groups  of  ex- 


Artificial  and  Natural  Selection        815 

ternal   causes.      First   come   those   that   have 
influenced    the    young    germs    of    the    plant 
during   its   most    sensitive   period,   when   still 
an  embryo  within  the  ripening  seed.       They 
give    a   new    limitation    to    the    average    con- 
dition, which  once  and  forever  becomes  fixed 
for    this    special    individual.      In    the    second 
place    the    young    seedling    is    affected    dur- 
ing the   development   of  its  crown    of  leaves, 
and     of    its     roots,     by     numerous     factors, 
which  cannot  change  this  average,  but  may  in- 
duce deviations  from  it,  increasing  or  decreas- 
ing the  amount  of  sugar,  which  will  eventually 
be  laid  down  in  the  root.    The  best  young  beet 
may  be  injured  in  many  ways  during  periods  of 
its  lifetim^e,  and  produce  less  sugar  than  could 
reasonably  be  expected  from  it.     It  may  be  sur- 
passed by  beets   of  inferior  constitution,  but 
growing  under  more  favorable  circumstances. 

Considered  from  this  point  of  view  the  result 
of  the  polarization-test  is  not  a  single  value,  but 
consists  of  at  least  two  different  factors.  It 
may  be  equal  to  the  algebraic  sum  of  these,  or 
to  their  difference,  according  to  whether  the 
external  conditions  on  the  field  were  locally  and 
individually  favorable  or  unfavorable.  A  large 
amount  of  sugar  may  be  due  to  high  individual 
value,  with  slight  subsequent  deviation  from  it, 


816  Fluctuations 

or  to  a  less  prominent  character  combined  with 
an  extreme  subordinate  deviation. 

Hence  it  is  manifest  that  even  the  results 
of  such  a  highly  improved  technical  method  do 
not  deserve  the  confidence  usually  put  in  them. 
They  are  open  to  doubt,  and  the  highest  figures 
do  not  really  indicate  the  best  representatives 
of  the  race.  In  order  to  convey  this  conception 
to  you  in  a  still  stronger  manner,  let  us  consider 
the  partial  variability  as  it  usually  shows  itself. 
The  various  leaves  of  a  plant  may  noticeably 
vary  in  size,  the  flowers  in  color,  the  fruits  in 
flavor.  They  fluctuate  around  an  average,  which 
is  assumed  to  represent  the  approximate  value 
of  the  whole  plant.  But  if  we  were  allowed  to 
measure  only  one  leaf,  or  to  estimate  only  one 
flower  or  fruit,  and  be  compelled  to  conclude 
from  it  the  worth  of  the  whole  plant,  what  mis- 
takes we  could  make!  "VVe  might  indeed  hit 
upon  an  average  case,  but  we  might  as  easily 
get  an  extreme,  either  in  the  way  of  increase 
or  of  decrease.  In  both  cases  our  judgment 
would  be  badly  founded.  Now  who  can 
assure  us  that  the  single  root  of  a  given 
beet  is  an  average  representative  of  the  partial 
variability?  The  fact  that  there  is  only  one 
main  root  does  not  prove  anything.  An  annual 
plant  has  only  one  stem,  but  a  perennial  species 
has  many.     The  average  height  of  the  last  is  a 


Artificial  and  Natural  Selection        817 

reliable  character,  but  the  casual  height  of  the 
former  is  very  uncertain. 

So  it  is  with  the  beets.  A  beet  may  be  di- 
vided by  its  buds  and  give  quite  a  number  of 
roots,  belonging  to  the  same  individual.  These 
secondary  roots  have  been  tested  for  the 
amount  of  sugar,  and  found  to  exhibit  a  man- 
ifest degree  of  variability.  If  the  first  root 
corresponded  to  their  average,  it  might  be  con- 
sidered as  reliable,  but  if  not  anyone  will  grant 
that  an  average  is  more  reliable  than  a  single 
determination.  Deviations  have  as  a  fact  been 
observed,  proving  the  validity  of  our  assertion. 

These  considerations  at  once  explain  the  dis- 
appointment so  often  experienced  by  breeders. 
Some  facts  may  be  quoted  from  the  Belgian  pro- 
fessor of  agriculture  at  Gembloux,  the  late  Mr. 
Laurent.  He  selected  two  beets,  from  a  strain, 
with  the  exceptional  amount  of  23^  sugar,  but 
kept  their  offspring  separate  and  analyzed  some 
60  of  each.  In  both  groups  the  average  was 
only  11  - 12^,  the  extremes  not  surpassing 
14-15^.  Evidently  the  choice  was  a  bad  one, 
notwithstanding  the  high  polarization  value  of 
the  parent.  Analogous  cases  are  often  observed, 
and  my  countrymen,  Messrs.  Kuhn  &  Co.,  go  so 
far  as  to  doubt  all  excessive  variants,  and  to 
prefer  beets  with  high,  but  less  extraordinary 
percentages.     Such  are  to  be  had  in  larger  num- 


818  Fluctuations 

bers  and  their  average  has  a  good  chance  of  ex- 
emption from  a  considerable  portion  of  the 
doubts  adhering  to  single  excessive  cases. 

It  is  curious  to  note  here  what  Louis  de  Vil- 
morin  taught  concerning  this  point  in  the  year 
1850.  I  quote  his  own  words:  ^'  I  have  ob- 
served that  in  experiments  on  heredity  it  is 
necessary  to  individualize  as  much  as  possible. 
So  I  have  taken  to  the  habit  of  saving  and  sow- 
ing separately  the  seeds  of  every  individual 
beet,  and  I  have  always  found  that  among  the 
chosen  parent-plants  some  had  an  offspring 
with  a  better  average  yield  than  others.  At  the 
end  I  have  come  to  consider  this  character  only, 
as  a  standard  for  amelioration." 

The  words  are  clear  and  their  author  is  the 
originator  of  the  whole  method  of  plant -breed- 
ing selection.  Yet  the  principle  has  been  aban- 
doned, and  nearly  forgotten  under  the  impres- 
sion that  polarization  alone  was  the  supreme 
guide  to  be  relied  upon.  However,  if  I  under- 
stand the  signs  rightly,  the  time  is  soon  coming 
when  Vilmorin's  experience  will  become  once 
more  the  foundation  for  progress  in  breeding. 

Leaving  the  theoretical  and  historical  as- 
pects of  the  problem,  we  will  now  recall  the  ex- 
perimental evidence,  given  in  a  former  lecture, 
dealing  with  the  inheritance  of  monstrosi- 
ties.    I  have  shown  that  in  many  instances  mon- 


Artificial  and  Natural  Selection        819 

strositieS  constitute  double  races,  consisting  of 
monstrous  and  of  normal  individuals.  At  first 
sight  one  might  be  induced  to  surmise  that  the 
monstrous  ones  are  the  true  representatives  of 
the  race,  and  that  their  seeds  should  be  ex- 
clusively sown,  in  order  to  keep  the  strain  up 
to  its  normal  standard.  One  might  even  sup- 
pose that  the  normal  individuals,  or  the  so-called 
atavists,  had  really  reverted  to  the  original 
type  of  the  species  and  that  their  progeny  would 
remain  true  to  this. 

My  experiments,  however,  have  shown  that 
quite  the  contrary  is  the  case.  No  doubt,  the 
seeds  of  the  monstrous  specimens  are  trust- 
worthy, but  the  seeds  of  the  atavists  are  not 
less  so.  Fasciated  hawkweeds  and  twist- 
ed teasels  gave  the  same  average  constitu- 
tion of  the  offspring  from  highly  monstrous, 
and  from  apparently  wholly  normal  indi- 
viduals. In  other  words  the  fullest  devel- 
opment of  the  visible  characteristic  was  not 
in  the  slightest  degree  an  indication  of  better 
hereditary  tendencies.  In  unfavorable  years  a 
whole  generation  of  a  fasciated  race  may  exhibit 
exclusively  normal  plants,  without  transmitting 
a  trace  of  this  deficiency  to  the  following  genera- 
tion. As  soon  as  the  suitable  conditions  return, 
the  monstrosity  reassumes  its  full  development. 

The  accordance  of  these  facts  with  the  ex- 


820  Fluctuations 

perience  of  breeders  of  domestic  animals,  and  of 
Louis  de  Vilmorin,  and  with  the  result  of  the 
theoretical  considerations  concerning  the  fac- 
tors of  fluctuation  has  led  me  to  suggest  the 
method  of  selecting,  which  I  have  made  use  of  in 
my  experiments  with  tricotyls  and  syncotyls. 

Seedling  variations  afford  a  means  of  count- 
ing many  hundreds  of  individuals  in  a  single 
germinating  pan.  If  seed  from  one  parent- 
plant  is  sown  only  in  each  pan,  a  percentage- 
figure  for  the  amount  of  deviating  seedlings 
may  be  obtained.  These  figures  we  have  called 
the  hereditary  percentages.  I  have  been  able  to 
select  the  parent-plants  after  their  death  on 
the  sole  ground  of  these  values.  And  the  re- 
sult has  been  that  from  varieties  which,  on  an 
average,  exhibited  50  -  55^  deviating  seedlings, 
after  one  or  two  years  of  selection  this  propor- 
tion in  the  offs]3ring  was  brought  up  to  about 
90^  in  most  of  the  cases.  Phacelia  and  mercury 
with  tricotylous  seedlings,  and  the  Eussian 
sunflower  with  connate  seed-leaves,  may  be 
cited  as  instances. 

Besides  these  tests,  others  were  performed, 
based  only  on  the  visible  characters  of  the  seed- 
lings. The  result  was  that  this  characteristic 
was  almost  useless  as  a  criterion.  The  atavists 
gave,  in  the  main,  nearly  the  same  hereditary 
percentages  as  the  tricotyls  and  syncotyls,  and 


Artificial  and  Natural  Selection        821 

their  extremes  were  in  each  case  far  better  con- 
stituted than  the  average  of  the  chosen  type. 
Hence,  for  selection  purposes,  the  atavists  must 
be  considered  to  be  in  no  way  inferior  to  the 
typical  specimens. 

If  it  had  been  possible  to  apply  this  principle 
to  twisted  and  fasciated  plants,  and  perhaps 
even  to  other  monstrosities,  I  think  that  it  will 
readily  be  granted  that  the  chance  of  bringing 
even  these  races  up  to  a  percentage  of  90;^ 
would  have  been  large  enough.  But  the  large 
size  of  the  cultures  required  for  the  counting  of 
numerous  groups  of  offspring  in  the  adult  state 
has  deterred  me  from  making  such  trials.  Ee- 
cently  however,  I  have  discovered  a  species, 
Viscaria  oculata  which  allows  of  counting 
twisted  specimens  in  the  pans,  and  I  may  soon 
be  able  to  obtain  proofs  of  this  assertion.  The 
validity  of  the  hereditary  percentage  as  a  stand- 
ard of  selection  has,  within  the  last  few  years, 
been  recognized  and  defended  by  two  eminent 
breeders,  W.  M.  Hays  in  this  country  and  Von 
Lochow  in  Germanv.  Both  of  them  have  start- 
ed  from  the  experience  of  breeders  of  domestic 
animals.  Von  Lochow  applied  the  principle 
to  rye.  He  first  showed  how  fallacious  the 
visible  characters  often  are.  For  instance 
the  size  of  the  kernels  is  often  dependent  on 
their  number  in  the  head,  and  if  this  number  is 


822  Fluctuations 

reduced  by  the  injurious  varietal  mark  of  la- 
cunae (Liickigkeit),  the  whole  harvest  will  rap- 
idly deteriorate  by  the  selection  of  the  largest 
kernels  from  varieties  which  are  not  quite  free 
from  this  hereditary  deficiency. 

In  order  to  estimate  the  value  of  his  rye- 
plants,  he  gathers  the  seed  of  each  one  separate- 
ly and  sows  them  in  rows.  Each  row  corre- 
sponds to  a  parent-plant  and  receives  200  or  150 
seeds,  according  to  the  available  quantity.  In 
this  way  from  700  to  800  parent-plants  are 
tested  yearly.  Each  row  is  harvested  sepa- 
rately. The  number  of  plants  gives  the  aver- 
age measure  of  resistance  to  frost,  this 
being  the  only  important  cause  of  loss.  Then 
the  yield  in  grain  and  straw  is  determined 
and  calculated,  and  other  qualities  are  taken 
into  consideration.  Finally  one  or  more  groups 
stand  prominent  above  all  others  and  are  chosen 
for  the  continuation  of  the  race.  All  other 
groups  are  wholly  excluded  from  the  **  elite," 
but  among  them  the  best  groups  and  the  very 
best  individuals  from  lesser  groups  are  consid- 
ered adequate  for  further  cultivation,  in  order 
to  produce  the  commercial  product  of  the  race. 
As  a  matter  of  fact  the  rye  of  Von  Lochow  is 
now  one  of  the  best  varieties,  and  even  sur- 
passes the  celebrated  variety  of  Schlanstedt.  It 
was  only  after  obtaining  proof  of  the  validity 


Artificial  and  Natural  Selection        823 

of  his  method  that  Von  Lochow  decided  to  give 
it  to  the  public. 

W.  M.  Hays  has  made  experiments  with  wheat 
at  the  Minnesota  Agricultural  Experiment 
Station.  He  chose  a  hundred  grains  as  a 
proper  number  for  the  appreciation  of  each 
parent-plant,  and  hence  has  adopted  the  name 
of  ^^centgener  power"  for  the  hereditary  per- 
centage. 

The  average  of  the  hundred  offspring  is  the 
standard  to  judge  the  parent  by.  Experience 
shows  at  once  that  this  average  is  not  at  all  pro- 
portional to  the  visible  qualities  of  the  parent. 
Hence  the  conclusion  that  the  yield  of  the 
parent-plant  is  a  very  uncertain  indication  of  its 
value  as  a  parent  for  the  succeeding  generation. 
Only  the  parents  with  the  largest  power  in  the 
centgener  of  offspring  are  chosen,  while  all 
others  are  whollv  discarded.  Afterwards  the 
seeds  of  the  chosen  groups  are  propagated  in 
the  field  until  the  required  quantities  of  seed  are 
obtained. 

This  centgener  power,  or  breeding-ability,  is 
tested  and  compared  for  the  various  parent- 
plants  as  to  yield,  grade,  and  percentage  of  ni- 
trogenous content  in  the  grain,  and  as  to  the 
ability  of  the  plant  to  stand  erect,  resist  rust, 
and  other  important  qualities.  It  is  evident  that 
by  this  test  of  a  hundred  specimens  a  far  liotter 


824  Fluctuations 

and  much  more  reliable  determination  can  he 
made  than  on  the  ground  of  the  minutest  exam- 
ination of  one  single  plant.  From  this  point  of 
view  the  method  of  Hays  commands  attention. 
But  the  chief  advantage  lies  in  the  fact  that  it  is 
a  direct  proof  of  that  which  it  is  desired  to 
prove,  while  the  visible  marks  give  only  very  in- 
direct information. 

Thus  the  results  of  the  men  of  practice  are  in 
full  accordance  with  those  of  theory  and  scien- 
tific experiment,  and  there  can  be  little  doubt 
that  they  open  the  way  for  a  rapid  and  impor- 
tant improvement.  Once  attained,  progress 
however,  will  be  dependent  on  the  selection- 
principle,  and  the  hereditary  percentage,  or 
centgener  power  or  breeding-ability,  must  be  de- 
termined in  each  generation  anew.  Without 
this  the  race  would  soon  regress  to  its  former 
condition. 

To  return  to  our  starting  point,  the  compari- 
son of  artificial  and  natural  selection.  Here  we 
are  at  once  struck  by  the  fact  that  it  is  hardly 
imaginable,  how  nature  can  make  use  of  this 
principle.  In  some  measure  the  members  of  the 
best  centgener  will  manifestly  be  at  an  advan- 
tage, because  they  contain  more  fit  specimens 
than  the  other  groups.  But  the  struggle  for 
existence  goes  on  between  individuals,  and  not 
between  groups  of  brethren  against  groups  of 


Artificial  and  Natural  Selection        825 

cousins.  In  every  group  the  best  adapted  in- 
dividuals will  survive,  and  soon  the  breeding- 
differences  between  the  parents  must  vanish 
altogether.  Manifestly  they  can,  as  a  rule, 
have  no  lasting  result  on  the  issue  of  the  strug- 
gle for  existence. 

If  now  we  remember  that  in  Darwin's  time 
this  principle,  breeding-ability,  enjoyed  a  far 
more  general  appreciation  than  at  present, 
and  that  Darwin  must  have  given  it  full  consid- 
eration, it  becomes  at  once  clear  that  this  old, 
but  recently  revived  principle,  is  not  adequate 
to  support  the  current  comparison  between  ar- 
tificial and  natural  selection. 

In  conclusion,  summing  up  all  our  arguments, 
we  may  state  that  there  is  a  broad  analog>^  be- 
tween breeding-selection  in  the  widest  sense  of 
the  word,  including  variety-testing,  race-im- 
provement and  the  trial  of  the  breeding-ability 
on  one  side,  and  natural  selection  on  the  other. 
This  analogy  however,  points  to  the  impor- 
tance of  the  selection  between  elementary  spe- 
cies, and  the  very  subordinate  role  of  intra- 
specific  selection  in  nature.  It  strongly  sup- 
ports our  view  of  the  origin  of  species  by 
mutation  instead  of  continuous  selection.  Or, 
to  put  it  in  the  terms  chosen  lately  by  Mr. 
Arthur  Harris  in  a  friendly  criticism  of  my 
views:  "  Natural  selection  may  explain  the  sur- 


826 


Fluctuations 


vival  of  the  fittest,  but  it  cannot  explain  the  ar- 
rival of  the  fittest/' 


f 


■• 


INDEX 


Abies  concolor  fastigiata,  618 
Acacia,    176,    196,    217,    458, 
697 

bastard,  343,  617,  618,  664, 
665,  666 
Acer  compestre  nanum,  613 
Achillea  millefolium,  131,  132, 

441 
Adaptation,  702 

double,   430,  451,  452,  454, 
455,  457,  458,  643 
Aegilops  ovata,  265 

spelt aeformis,   265 
Agave  vivipara,  684 
Ageratum  coeruleum,  613 
Agrostemma      Coronaria      hi- 
color,   125 

Githago,  282 

nicaeensis,  163 
Agrotis,  204 

Alder,   cut-leaved,    147,   596 
Alfalfa,  264 
Algae,  699 
Allen,  Grant,  237 
Alliaria,   638 

Alnus  glutinosa  laciniata,  615 
Alpine  plants,  437,  695,  794 
Althaea,  490 
Amaranth,   282,   453 
Amaranthus  caudatus,  282 
Amaryllis,  272,  275,  762 

brasiliensis,  275 

leopoldi,  275 

pardina,  275 

psittacina,  275 

vittata,  275 
Amen-Hotep,  697 
Ampelopsis,  239 
Amygdalus  persica  laevis,  126 

827 


Anagallis  arvensis,  162 
Androsace,  634 
Anemone,  266,  331 

coronaria,     241,     491     var. 

"Bride,"    510 
magellanica,  266 
sylvestris,   266 
Anemone,  garden,  241 
Annee,  760 
Anomalies,    taxonoraic,    658- 

685 
Anthemis,  236 
nobilis,  130 
Anthurium  scherzerianum ,  639 
Antirrhinum  ma  jus,  315 

luteum  rubro-striatum ,  315 
Apetalous  flowers,  622 
Apples,    134,    240,    328,    454, 
806 
elementary  species,  75 
method  of  cultivating,  76 
origin   of   cultivated   varie- 
ties, 73 
use  by  the  Romans,  74 
"  Wealthy,"  78,  79 
wild,  73,  74,  75,  76 
Aquilegia  chrysantha,   161 
Arabis  ciliata  glabrata 

hirsuta  glaberrima,    126 
Aralia  crassifolia,  663 
Arbres    fruitiers    ou    Pomon- 

omie  beige,  76 
Aralia  papyrifera,  663 
Arctic  flora,  695 
Arnica,  494 

montana,  236 
Aroids,  222,  631,  639 
Artemisias,  131 
Artificial  selection,  18.  71.  77, 
93,    95,    743,    744,     798- 
826 


828 


Index 


first  employed,  72,  92 
nature  of,  19 
Arum    maculatuni    immacula- 

Aseidia,'310,    366,    367,    427, 
428,    669,   670,   671,    672, 
673,  674,  675 
Ash,  135,  341 

one-bladed,  666,  667 
weeping.  196,  596 
Ashe,  343 
Aster,  132,  152,  242 

seashore,  200,  282* 
Aster    Tripolium,     132,     200, 

236,  282,  410 
Astragalus  alpinus,  696 
Atavism,   154,    170,    172,    175, 
176,    178,    182,    185,    187, 
188,    198,    220,   222,   226, 
235,    344,    354,   399,   405, 
411,  660,  661 
bud,  183,  226 
definition   of,   170,  631 
false,  185,  187 
negative,  344 
positive,  344 
seed,  176 

systematic,    174,    222,    630- 
657 
Atavists,  156,  201 
heredity  of,  413 
Atropa  Belladonna  lutea,  592 
Aubretia,  241 
Avena  fatua,  100,  207 
Azalea,  178,  323 
Azolla  caroliniana,  239 

B 

Babington,    Manual    of    Brit- 
ish Botany,   36 
Bailey,  78,  306,  684 
Balsams,  334 
Bananas,  90,  134 
Banyan.  244 
Barberry,  133,  180 

European,  270 

purple,  596 
Barharea  vulgaris,  427 
Barley,  98,  105,  133,  203,  678, 
679 


"Nepaul,"    203,    676,    677, 
679,  681,  683 
Bastard-acacia,   133,   136,   140 
Bateson,  250 
Bauhin,  Caspar,  72,  610 
Baumann,  618 

Beans,  90,  152,  327,  727,  735 
Bedstraw,  648 
Beech,  133,  135,  243 

cut-leaved,   179,    196,  616 

laciniated,  196 

oak-leaved,  595 

purple,    196,   593,   595 
Beeches,  427 

fern-leaved,  147 
Beets,  68,  72,  92,  93,  792,  796, 
801,  815,  817,  818 

Californian,  796 

European,  796 

forage,  71,  72,  791 

salad,  71 
Beet-sugar,  67,  68,  69,  70,  71, 
109,    165,    717,    791,    807, 
813,   814 
Begonia,  218,  366,  509,  765 

ever-flowering,   148 

tuberous,  272 

clarkii,  273 

davisii,  273 

rosiftora,  273 

sedeni,  273 

semperflorens,  133,  148,  620 

Begonia 

bulbous,   372 

veitchi,  273 
Behrens,  804 
Belladonna,  145 
Bellis  perennis,  236 

perennis  plena,  195 
Bentham,  237 
Bentham  &  Hooker 

Handbook  of  British  Flora, 
36 
Berhens,  133,  180,  455 

ilicifolia,  270 

vulgaris,  270 
Bertin,  596 

Berula  atigustifoUa,  457 
Bessey,  660 
Beta  maritima,  69 


Index 


829 


patula,  69,   70 
vulgaris,  69,  70 
Betula,   133 
Between-race,  358 
Bewirkung,    Theorie    der    di- 

recten   (Nageli),448 
Biastrepsis,  402 
Bidens,  131 

atropurjmrea,  131 
cernua,   131,  158 
leucantha,  131 
tripartita,  131 
Bilberries,  577 
Bindweed,  419,  424 
Binomium,  of  Newton,  767 
Birch,  133,  243 

cut-leaved,  596,  616 
fastigiate,  618 
fern-leaved,  179 
Biscutella,  283 

laevigata  glabra,  125 
Bitter-sweet,  125 
Blackberry,  268,  768 

"Paradox,"  769 
Blue-bells,    variation    in,    54, 

491,  577 
Blueberries,  769 
Blue-bottle,  499,  507,  509,  510 
Blueflag,  atavism  of,  173 
Boehmeria,  675 

bilhoa,  685 
Bonnier,   439,   441,   442,    444, 

451,  795 
Boreau,  663 

Brambles,  126,   127,  147,  239, 
244,    245,    L68,    740,    769, 
663 
Brassica,  244 
Braun,  738 

Braun  and  Schimper,  494 
Bread-fruits,   90 
Briot,  618 
Britton    and    Brown's    Flora, 

162 
Brooks,  711 
Broom,  140 

prickly,   217 
Broom-rape,  220 
Broussonetia     papyifera     dis- 

secta,  616 


Brunella,  146,  268 
vulgaris,  577 
vulgaris  alba,  201 
Bryophyllum  calycinum,  218 
Buckwheat,  453 
Bud-variation,  750 
Buds,    adventitious,   218 
Burbank,  Luther,  57,  79,  116, 
134,    268,    758,   768,    769, 
784 
Buttercup,  331,  357,  410,  725, 
740 
Asiatic,  241 


Cabbages,  428,  684 

atavism  in,  638 

origin  of  varieties,  621 
Cactuses,  444 
Cactus-dahlia,  625 
Calamintha  Acinos,   437,   453 
Calamus  root,  222 
Calendula  officinalis,  503 
CalUopsis  tinctoria,  195 
Calluna,  146 

vulgaris,  437,  577 
Caltha,  490 

palustris,  331 
Camelina,  684 
Camellia,  178,  323 

japonica,  368 
Camellias,   331 
Camomile,  130,  132,  156,  366, 

494,  503,  509,  513 
Campanula    persioifolia,    161. 

234 

rotundifolia,  437 
Campion,  283,  302,  304 

evening,  281 

red,  238 
Canna,  751,  759,  761 

indica,  760 

"  Madame  Crozy,"  760.  701 

nepalensis,  760 

icnrozeu'iczii,  760 
Capsella    Bursa-pastoris    ape- 
tala,  585 

heegeri,  22,  582,  583,  084 
Car  ex,  53 


830 


Index 


Carnation,   178,  241,  491 

wheat-ear,  227 
Carpinus       Betulus       hetero- 

phylla,  180 
Carriere,  491,  596,  612,  806 
Carrots,  806 
Catch-fly,  419 

Carboniferous    period,    699 
Casuarina  quadrivalvis,  649 
Cauliflowers,  origin  of,  621 
Caumzet,    614 
Causation,    theory    of    direct, 

(Nageli),  448 
Cedar,    pyramidal,   618 
Celandine,  147,  245,  280,  365 

oak-leaved,  603,  610,  611 
Celosia,  621 

Celosia  cristata,  327,  411 
Centaurea,  242 
Centgener  power,  20,  823 
Centranthus  macrosiphon,  424 
Cephalotaocus ,  170,  226 

pedunculata  fastigiata,  169 
Cereals,    105,    106,    107,    119, 
801,  804 

origin  of  cultivation,  104 
Character-units,  633 
Charlock,  424 
Cheiranthus,  490 

Cheiri,  370 

Cheiri  gynantherus,  371 
Chelidonium    laciniatum,    22, 
609 

ma  jus,   147,   365,  600,   610, 
611 

ma  jus  foliis  queznis,  610 
Cherries,  79 
Cherry,  bird's,  617 
Chestnuts,  427 
Chromosomes,   306 
Chrysanthemum,  178,  274 

corn,  739 
Chrysanthemum       carinatum, 
494 

coronarium,    161,    202,    510 

grandiflorum,  739 

imbricatum,  494 

indicum,  490 

inodorum,  503 


inodorum  plenissimum,  366 

new    double,    501 

segetum,  202,  493,  504,  729 

segetum,  var.  grandifioruMi^ 
43,  495,  498,  504,  504 
Chrysopogon  montanus,  450 
Cieslar,    804 
Cineraria  cruenta,  514 
Cinquefoil,  53 
Clarkia,  420 

elegans,  198 

pulchella,  282 

pulchella   carnea,    163 
Clematis    Vitalba,   663 

Viticella  nana,  613 
Clover,  80,  102,  674 

crimson  (Italian),  353,  358, 
359,  360 

five-leaved,    340,    362,    374, 
431,  509,  789 

four-leaved,  340,  346,  353 

red,  235,  281 

white,  133,  366 
Clusius,  610 
Cochlearia  anglica,  52 

danica,  52 

officinalis,  52 
Coconut,   67,   82,   83,   87,   88, 
89 

dispersal  of,  85,  89 

geographic  origin  of,  88,  89 
Coconut-palm,  84,  88 
Coekerell,  T.  D.  A.,  139,  140, 

591 
Cocklebur,  139 
Cockscomb,  165,  327,  356,  411, 

621 
Cocos  nucifera  stupposa,   83, 
84 

cupuliformis,  83 

rutila,  83 
Codiaeum        appendicularum, 

673 
Colchium,  490 
Coleus,    133 
Columbine,  725 

yellow,    161 
Columbus,  89,   118 
Columella,  106 


Index 


831 


Composites,     130,     131,     336, 

723,  778 
Conifers,  168,  226,  239,  455 

weeping,  617 
Connation,  of  petals,  660,  601 
"  Conquests,"  243 
Contra-selection,    425 
Cook,  84,  86,  88,  89 
Corn,   81,    90,    118,    119,    135, 
283,    287,   288,    775,   786, 
788,  804 

American,  205 
Corn-cockle,   163 
Corn-chrysanthemum,  739 
Corn-flowers,  491,  493 
Corn,  "Forty-day,"  118 

"Harlequin,"  327 

sterile  variety  of,  623 

sugar,  135,  158 

"Tuscarora,"  205 
Corn-marigold,  493,  494 
Cornel  berry,  yellow,  196 
Cornaceae,  675 
Cornu,  338 
Cornus  Mas,   196 
Correlation,    143 
Corylus,  133 

Avellana,   181 

tiibulosa,  181 
Cotton,  725 
Cotyledon,  674 

variation  in,  416 
Crambe  maritima,  621 
Cranesbill,   599 

European,  628 

meadow,  323 
Crataegus,   196 

oxyacoMtha,  133 
Crowfoot,   331 

corn,  283 
Crepis  biennis,  410,  411 
Cress,  Indian,  193 
Crosses 

bisexual,  255,  276,  294,  298 

reciprocal,  279 

unisexual,  255,  261 

varietal  (see  Hybrids). 
Croton,  673,  674 
Crozy,  760,  762 
Crucifers,  222,  635 


Cryptomeria,  109,  226 

japonica,  239 
Cucumbers,   118 
Cucumis,    52 
Cucurbita,   52 
Cultivated  plants,  65,  60 

elementary  species  of,  63 

improvement   of,    92 

mixed  nature  of,  90,  118 

origin    of,    91 
Currants,  79 

Californian,   270 

flowering,    166 

"Gordon's,"  270 

Missouri,  270 

white,    158 

white-flowered,  167 
Cuttings,  721 
Cyclamen,  323,  355,  627,  684 

Butterfly,  627 

vernum,  619 
Cypripedium    caudatum,    487 
Cytisus  adami,  271 

candicans    Attleyaniis,    307 

Laburnum,  271 

prostratus,  139 

prostratus  ciliata,    125 

purpureus,  271 

spinescens,  139 


Dahlia,  131,  241,  272,  625 

cactus,   625 

"  Jules  Chretien,"  628 

purple-leaved,  626 

"  surprise,"  230 

tubular,  627 

274,  490,  764 

first  double  ones,  490 

green,   227,  229,  230 
Daisies,  131,  132,  494 

double,  195 

hen-and-chicken,  514 

ox-eye,  202 

Shasta,  769 

yellow,   202 
Dandelion,  411 

parthenogenesis,   0 1 

variations  in,  00 


832 


Index 


Daphne  Mezereum,  146 
Darwin,    1,   2,    3,   4,   b,   6,    7, 
18,   76,   85,   93,   109,   110, 
180,    196,    205,   206,    242, 
306,    324,    338,   448,    571, 
604,    612,    689,    702,    710, 
715,  743,  798,  825 
Darwin,  George,  711 
Darwinian  theory,   461 

basis    of,    5 
Date,   134 
Datura  Stramonium,  139,  142 

Stramonium,  inermis,  300 

Tatula,  139,  142,  300 
Dead-nettle,  237 
De  Bary,  38,  47,  49 
De   Candolle,   76,   84,   85,   89, 
228,  370,  403,  621 

Alphonse,  74,  129,  226 

A.  P.,  129 

Casimir,  659,  676 
De  Graaff,  275 
Delphinium  Ajacis,  192 
Deniaii,  617 
Descent,  theory  of,  690,   694, 

702,  707,  716,  798 
De  Serres,  Olivier,  72 
Desmodium  gyrans,  655,  656, 

663,    664,    65 
Dewberry,   California,   269 
Dianthus   barhatus,    322,    648 

twisted  variety,  408 
Diatoms,  699 
Dictoyledons 

ancestors        of        monocot- 
yledons, 15 
Digitalis  parvifiora,    161,   640 

purpurea,  483 

pelorism  of,  483 
Dimorphism,    445,    447,    454, 

457,  458 
Dippe,  810 
Dipsacus  fullonum,  402 

sylvestris,  402,  403 
Dominant  character,   280 
Double  flowers 

poppies  490 

production  of,  489 

types  of,  330 
Double  races    (see   also  ever- 


sporting   varieties),    419, 
427,  428 
Dubois,  Eugene,  712 
Duchesne,  185,   188,  596 
Duckweed,   222 
Draba,  692,  693 

verna,  47,  50,  51,  53,   125, 
126,    518,    533,   546,    547, 
561 
Dracocephalum      moldavicum, 

419 
Dragon-head,  419 
Drosera  anglica,  268 
filiformis,    268 
intermedia,  268 
obovata,  267 
rotundifolia,  268 


E 


Earth,  age  of,  710 
Edelweiss,  438 
Eichler,  660 
Election,  801 

Electric  light,  growth  in,  442 
Elementary  species,  11,  13,  32, 
67,  74,  76,  77,  78,  79,  91, 
95,    116,    119,    124,    126, 
128,    129,   207,    238,    252, 
256,    307,   430,    435,    695, 
696,    698,    702,   715,    787, 
798,  800,  825 
apples,  75 
coconut,    82 
corn,   81 

cultivated  plants,  63 
definition  of,  12,  35,  127 
flax,   80 

how   produced,   16,  248 
hybrids  of,  253,  255 
mutation   of,    141 
origin  of,  459,  603 
origin  of,  how  studied,  463 
selection  of,  92 
varieties    vs.,    14,    15,    141, 
152,    224,    243,    247,    251, 
495 
Elm,  136,  219,  239,  427 
Epilobium,  268 
hirsutum,  683 


Index 


833 


hirsutum  cruciatum,  588 
montanurriy  269 
tetragonum,  269 
Equisetum     Telmateja,     642, 

649 
Erica  TetralioOy  577,  661 
Ericaceae,  146,  660 
Erigeron  aster oides,  450 
canadensis,    132,    236,    453, 
600,  695 
Erodium,  146 
Erodium    cicutarium    alhum, 

161 
Erucastrum,  630,  638,  639 

pollichii,  222,  637 
Eryngium   campestre,    674 

maritimum,  674 
Erysimum  cheiranthoides,  638 
Erythraea  pulchella,  453 
Erythrina,  621 

Crista-galli,  620 
Eschcholtzias,  59 
Esimpler,  337 
Eucalyptus  citriodora,  669 

Globulus,  217 
Euphorbia  Ipecacuanha,  55 
Evening-primrose,    62,    204, 
256,    424,    686,    687,    688, 
690,    691,    694,    695,    699, 
702,    703,    705,    707,    708, 
713   747    793 
Evolution,  93,  685,  686,  689, 
704,   707,   709,    710,   713, 
718 
degressive,  222,  223,  249 
progression  in,  630 
progressive,    221,   222,   223, 

248 
regression  in,  630 
regressive,    221,    222,    223, 

249 
retrograde,   221,  631 
Extremes,     asexual    multipli- 
cation of,  742,  769 


P 


Fabre,  265 
Fagus,  133 


Fagus  sylvatica  pectinata,  179 
Fan,  genealogical,  700 
Fasciated  stems,  409,   413 
Ferns,  63 
cristate,  427 
plumose,  427 
Ficaria,  53 
Ficus  radicans,  436 
religiosus,  244 
repens,  436 
stipulata,  436 
ulmifolia,  436 
Figs,  436 
Filago,  53 
Fir,  134,  804 
Fittest,  survival  of,  826 
Flax,  80,  805 
springing,  80 
threshing,    80 
white-flowered,  158,   160 
Fleabane,    Canada,    132,    236, 

600 
Flowers,  gamopetalous,  660 
Fluctuability 

embryonic,  see  individual 
Fluctuation,     708,    715,    716, 
718,  719,  724,  737,  741 
curves  of,  729,  734 
defined,    191 
individual,    718,    723,    732, 

741,  745,  749,  788 
mutation  vs.  7,  16,  719 
partial,  718,  723,  732,  741, 

745,  748,  749,  771 
inadequate     for     evolution, 

18 
in  elementary  species,  19 
nature  of,  18 

specific   and    varietal    char- 
acters vs.  17 
Forget-me-not,   308 
Fothergill,  John,  521 
Foxglove,  163 

peloric,    164,  356,  367 
yellow,  161,  640 
Fraxinus      excelsior      mono- 
phylla,  667 

exhcterophi/Ua,  667 
simplicifolia,  607 


834 


Index 


1 


French    flora     (Grenier    and 

Godron),  433 
Fries 

on   Hieracium,   60 
Frostweed,   440 
species  of,   53 
Fuchsia,   272,    355 
Fuchsias,  491 


G 


Gaertner,  279 

Galeopsis  Ladanum  canescens, 

139 
Galium,  648 

Aparine,  409,  648 

elatum,  52 

erectum,  52 

Mollugo,  52 

verum,  648 
Gallesio,  138 
Gallon,  736,  776 
Gamopetaly,   663 
Garden-pansy,    origin    of,    38 
Garlic,   638 
Gaiichery,  453 
Geikie,  711 
Genera 

artificial  character  of,  36 

polymorphous,  693 
Gentiana    punctata    concolor, 

125 
Gentians,   577 
Georgics    (Vergil),    106 
Geranium  pratense,  323,  628 

album,  628 

pyreniacum,  599 
German  flora   (Koch),  433 
Geum,  282 
Gherkins,   118 
Gideon,  Peter  M.,  78 
Glacial   period,   696 
Gladiolus,  241,  272,  274,  368, 
765 

cardinalis,  275 

gandavensis,  275 

psittacinus,  275 

purpureo-auratus,  275 
Glaucium,  241 
Gleditschia  sinensis,  614 


triacanthos  pendula,  617 
Gloxinia,  282,  485 

erect,   626 
Gloxinia  erecta,  485 

peloric  variety,  485 
Gnaphalium       Leontopodium, 

438 
Godetia  amoena,  161 
Godetias,  59,  232 
Godron,  265,  433 
Goeppert,   370 
Gooseberry,    79,    140,    626 

red,  133,  165,  241 
Grapes,  90,  158,  328 
Grape-hyacinth,  plumosa,  134 
Grasses,  102,  631,  681 
Grenier,  433 
Groundsel,  132 
Growth,    nutrition   and,    714, 

720,   722 
Guelder-rose,  134,  239 
Gum-tree,  Australian,  217 
Gypsophila   paniculata 

twisted  variety,  409 


H 


Haeckel,  707 

Half-races,  358,  372,  409,  419, 

424,  427,  428 
Hall,  444 
Hallet,  F.  F.,  109 
Harebell,  232 

peach-leaved,  234 
Harris,  Arthur,  825 
Harshberger,  John  W.,  591 

on  Euphorbia  in  New  Jer- 
sey, 55 
Hawksbeard,   410,  411,  412 
Hawkweed,  411  439,  443,  819 
Hawkweeds. 

seeding    without    fertiliza 
tion,  61 
Hawthorn,  white,   133 
Hays,  W.  M. 

on  individual  selection,  20, 
94,  95,  117,  821,  823,  824 
Hazelnut,   133,   181,  243 
Hazels,  cut-leaved,  596,  616 
Heath   family,   146,   222,   660 


Index 


835 


Heaths,   origin   of,  662 
Heather,  577 

Hedera  Helix  arhorea,  437 
Hedgehog    burweed,    140 
Hedysarum,    664 
Heeger,  582 
Heer,  Oswald,  74j  105 
Heinricher,    172,    173,    174 
Helianthemum,  53,    125,    126, 
561 

apenninum,  53 

pilosum,  53 

polifolium,  53 

pulverulentum,  53 

vulgare,  440 
Helichrysum,  420 
Heltoingia,  678,  678,  683 

ruscifiora,  675 
Hemp,    419 
Henbane,   283 
Bepatica,  322,  490 
Heredity,  731,  734,  818 

bearers   of,  632 

in  teasels,  643 
Hesperis,  241,  322 

matronalis,  323,  411 
Eeylandia   latebrosa,  450 
Hibiscus  Moscheutos,  591 
Hieracium,  59,  439 

alpinum,  698 
Hildebrand,   160,  240,   241 
Hoffman,   160,  663 
Hofmeister,    160,   370,  480 
Holbein,  164,  596 
Holly,  140,  196 
PToltermann,  449,  451 
Hollyhock,  427 
Honeysuckle,   674 

ground,  443 
Hordeum  distichum,  677 

hexastichum,    677,    678 

tetrastichum,    677 

trifurcatum,  676,  678 

vulgare   trifurcatum,   203 
Hornbeam,   European,    180 
Horse-chestnut,  219 

thornless,  234 
Horsetail,  Canadian,   695 

European,  649 


Horsetail,  family,  641 
Horse- weed,    132 
Canadian,  453 
Hortensia,   134,   181 
Horticulture,     mutations     in, 

604 
Houseleek,  370,  371 
Hunneman,  John.  521 
Hyacinths.  178.  323 

white,  160 
Hybrids,    58,    201,    202,    206, 
250,  575 
between  elementary  species, 

253 
constant,  263,  264,  265,  266, 

267,  268,  269 
law  of  varietal,  716 
Mendelian,  324 
nature   of,   20 
species,  256,  260 
splitting   of,    210 
varietal,  208,  209,  247    277, 
278,   279,    281,    285,    293, 
294 
Hybridization,  706,   751,  752, 

758,   759,   764 
Hydrocotyle,  668 
Hyoscyamus  niger,  283 

pallidus,  283 
Hypericum   perforatum,   725 
Hyssopus    officinalis,    161 


Iberis  umbellata  rosea,  195 
Improved    races,    inconstancy 

of 
Indian  cress,  668 

pelorism  of,  485 
Indian  pipe,  661 
Ipecac  spurge,  55 
Iris,  456 

falcifolia,   173 

kaempferi,  174 

lortetii,  521 

pallida,    173 

pallida    abavia,    681 
Isolation,    108 
Ivy,  436 


836 


Index 


Jacob's  ladder,  200,  202 

Jacques,  614 

Jacquin,  52,  633 

Jaggi,  594,  595 

Jaeger,  228,  663 

Jalappa,   165 

Janczewski,  266 

Japanese  plum,  58 

Jasminum   Samhac,   663 

Joly,   712 

Jordan,  Alexis,  45,  47,  49,  50, 

129 
experiments     with     species, 

37,  40 
J  uncus  effusus  spiralis,  684 
Juniper,  684 


K 


Kapteyn,  716 

Kelvin,  Lord,  710,  711 

Kerner    von    Marilaun,    266, 

267 
Keteleer,  618 
Knight,  390,  719,  720 
Koch,  433,  667 
Koelreuter,  279 
Korshinsky,     609,     612,     614, 

617,  667 
Krelage,  510,  619 
Kuhn    &    Co.,    Messrs.,    801, 

809,  817 


Labiates,  237 

pelories  of,   577 
Labiatiflorae,  pelorism  of,  468 
Labrador  tea^  661 
Laburnum,   270,   284,    343 

oak-leaved  147,  179 

pelorism  of,  485 
Lactuca,  52 

Soariola,  456 
Lagasca,  Mariano,  96,  97,  114 
Lamarck,  1,  447,  461,  522,  523 
Lamarckism 

objections  to,  449 


Lamium  album,  237 

maculatum,   237 

pelorism  of,  486 

purpureum,  237 
Larch,  804 
Larkspur,   124,   192,  311,  452 

hybrid,    213 

white,  160 
Latency,  657 

individual,  219 

specific,  246 

systematic,    219,   220,    235 

varietal,  246 
Latent  characters,  216 
Lathyrus   odoratus,   776 
Laurea  pinnatifida,   450 
Laurel,  lady's,  146 
Laurent,  802 
Leaves,  cleft,  685 

variegated,  426,  431 
LeBrun,  Mme.,  614 
Le  Couteur,  96,  97,  107,   108, 

114,  115,  116,  743 
Ledum,    222,    661 
Lemna,  222 
Lemoine,  762,  763 
Lettuce,  684 

crisped,  158 

prickly,  456 
Life,   struggle   for,    103,    119, 

120 
Lilacs,    59,    769 

double,  762 
Lilium  candidum  fiore  pleno, 
331 

pardalium,  116 
Lime-tree,  355,  366,  428,  669 

fern-leaved,  147 
Linaria,  467,  471,  480 

dalmatica,  482 

genistifolia,  267 

italica,  267 

vulgaris,  267,  471 

vulgaris   peloria,   464 
Lindley,  63,   129,   506 
Linnaeus,    32,    33,    129,    132, 
256,  663 

on  the  idea  of  species,   11, 
13 


Index 


837 


on  origin  of  species,  2,  34 

on  primroses,  52 
Linum  angustifolium,  80 

crepitans,  81 

usitatissimum,    80,    161 
Link,  466 
Liver-leaf,   322 
Lobelia  syphilitica^  161 
Lonicera  etrusca,  640 

tartarica  nana,  614 
Lorenz,  Chr.,  482 
Lothelier,  454 
Lotus  corniculatus,  443 

corniculatus  hirsutus^  139 
Loudon,  615,  616,  667 
Lucerne,  264 
Ludwig,  738 
Lupines,  90 
Lychnis,  283 

chalcedonica,   161 

diurna,  238,  578 

preslii,  578 

vespertina,  238,  281,  585 
Lycium,  455 
Ly coper sicum,  655 

grandifolium,  654 

latifolium    (see   L.    grandi- 
folium ) . 

solanopsis,  654,  656 

validum    (see    L.    solanop- 
sis). 
Lyell,  1,  710 
Lysimachia  vulgaris,  684 

M 

MacDougal,  D.  T.,  62,  575,  590 
Macfarlane,   56,   255,  268 
Madia  elegans,  779 
Magnolia,  355,  366,  428,  674, 
675 

ohovata,  355,  669 
Magnus,   228 
Mahonia    aquifolia,   270 
Maize,   134,   775 

"Cuzco,"    152 

European,   206 

"  Gracillima,"   152 

"  Horse-dent,"  152 

"  Quarantino,"  118 


Mallow,    663,    684 
Malva  crispa,   684 
Maples,  laciniate,  615 
Marchant,  592 
Marigold,  131,  158 

corn,  729 

field,  503,  505,  508 

garden,  503 

Japanese,    490,    494,    495 
Marsh-marigold,  331 
Martinet,  80 
Massart,  434 
Masters,  228,  370,  372 
Matricaria  Chamomilla,   130 

Chamomilla    discoidea,    156 
Matricaria   discoidea,    D.    C, 

157 
May-thorn,  red,  196 
Medicago  media,  264 

falcata,  264 
Melanimn,  39 
Melons,  118 
Mendel,  6,  210,  294,  296,  300, 


308 


Mendel's   law,  276,   293,   204, 
298,   299,    300,    301,   307, 
611,  613,  616,  716 
Mendelism,   307 
Mentha,  52 
Mercurialis  annua,  420 

annua  laciniata,  592 
Mercury,  420,  422,  425,  820 
Methods   of   investigation,   21 
Metzger,   205,  206 
Milde,   38 
Milfoil,  441 
Millardet,   266 
Miller,  611 
Millet,  105 
Mimulus,  151 

quinquevulnertis,  725 
Mimusops,  697 
Miocene  period,  698 
Miquel,  83 
Mirahilis,  241 

Jalappa,  322 
Mirbel,  615 

Monardella  macrnntha,  444 
Monstrosities,   400,   401,   445, 
446,  447 


838 


Index 


Monkey-flower,  725 
Monocotyledons 

ancestry  of,   15 

regression  in,  630 
Monotropa,  222,  661 
Morphologic  units,  145,  153 
Monstrosities,  818 
Morgan 

on  mutation-theory,  9 
Morren,  244,  763 
Mountain-ash,  342 
Muller,  Fritz,  775,  776,  780 
Multiplication,  vegetative  (see 

Asexual  propagation ) . 
Munting,  Abraham,   164,   165, 

490,  762 
Munting's   drawings,   512 
Murr,  158,   236 
Muscari  comosum,  134 
Museum  d'Histoire  Naturelle, 

Paris,   522 
Mutability  vs.  fluctuating  va- 
riability, 568 
Mutation,  659,  674,  677,  685, 
686,  694,  713,  716,  825 

absence      of      intermediate 
steps  in,  474,  480 

conditions     for     observing, 
601 

decided  within  the  seed,  28 

definition  of,  7 

easily  observed,   30 

experimental,   688 

few  observations   of,    8 

fluctuation  vs.,  7,  16,  719 

influence  of  on  variability, 
335 

iterative    nature    of,    476, 
703 

laws  of,  556,  558,  560,  562, 
564,  566,  568,  570 

limited  in  time,  29 

observation  of,   16 

in  Oenothera,  521,  525,  690 

oldest  known,  609 

oldest   recorded,   22 

periodic,  690,  692,  694 

perodicity  of,  519 

progressive,  307 

repetition  of,  476 


in  Saponaria  caldhrica,  612 

simultaneous,   614 

in  tomato,  655 
Mutations,  141,  275,  280,  445, 
449,    573,    608,    620,   626, 
678,    685,   686,   701,   704, 
712,  713,  716,  800 

artificial,   402 

chance  for  useful,  598 

defined,   191 

frequency  of,  597 

in  garden-flowers,  488 

in  horticulture,  604,  706 

latent,  703 

mode  of  appearance,  517 

numerical     proportion     of, 
475 

original  production  of,  703 

peloric,  707 

periodic,  686,  705 

progressive,   704 

retrograde,  704 

stray,  704,  705,  706 

synonyms  of,  191 
Mutation-period,    714 
Myosotis  azorica,  368 
Myrtus  communis,  684 


N 


Nageli,  60,  439,  443,  448,  795 

Nagelian  principle,  448,  450, 
451 

Natural    selection,     18,     119, 
120,    445,    456,   682,   694, 
703,  743,  744,  798-826 
basis,  604 
nature  of,  6,  19 

Naudin,  118 

Nectarines,  137,  138,  226,  627 

Ngmec,  578 

Neo-Lamarckians 
principle  of,  8 

Neo-Lamarckism     447 

'Nepenthes,  671,  672,  673,  674 

Newton,  1,  732,  767 

Nicandra,    152 

Nigella,   134 

Nightshade,  298 
black,   282 


Index 


839 


Nourishment 

meaning  of,  733 

variability  and  771 
Nuphar,  268 
Nutrition    and    growth,    720, 

722 
Nymphaea,  698 


O 


Oats,  98,    100,  101,   105,   112, 
113,  115,  119,  133,  453 

"Early  Angus,"  115 

"Early  Fellow,"  115 

"Fine  Fellow,"  115 

"Hopetown,"   112 

"Longfellow,"  115 

"  Make-him-rich,"  113 

wild,  207,  803 
Oak,  136,  239 

Oenothera,  260,  262,  279,  700, 
706,  708,  709 

European  species,  source  of, 
575 

mutation  in,  521,  525,  585, 
690,   708 

new  species  of,  516-546 

albida,  537,  553,  555,  563, 
565,   573 

Uennis,  62,  205,  256,  257, 
258,  259,  262,  263,  264, 
521,  524,  527,  574,  575, 
586,  587,  683,  690^  708 

biennis  cruciata,  22,  587 

brevistylis,  263,  280,  526, 
529,    530,    547,    563,    564, 

565,  573,    574,    702,    706 
cruciata,  575,  585,  586,  589, 

590,  683 
elliptica,  540,  545,  555,  563 
gigas,    533,    534,    535,    536, 

537,   553,    554,   563,    565, 

566,  567,  573,  574,  703 
glauca,  424 

hirtella,   263 

laevifolia,     526,     528,    529, 

547,    563,    564,   573,   574, 

701,  706 
lamarckiana,    17,    262,    263 
522,     523,    527,    528,     529, 


533,    574,    575,    586,    090, 
699 

pollination  of,   524. 
lata,  540,  541,  542,  549,  550, 
551,    552,    555,    559,   563, 
566,    573,    574,    703 
leptocarpa,  540 
muricata,     256,     257,     258, 
259,   262,   263,    264,    513, 
675,  690 

pollination   of,   524. 
nanella,   526,   531,   549,   50, 
551,    552,    555,    563,    564, 
565,   566,   703 
oblonga,  537,  538,  552,  555, 

563,    565,    566,    573 
rubrinervis,   533,   534,   536, 
537,   550,    551.    552,    555, 
563,  565,  568,  573,  574 
scintillans,    540,    543.    553, 
555,  563,  566,  573,  574 
mutability  of,  544 
semilata,   540 
suaveolens,  521 
Oleander,  684 
Onagra,  262,  708,  709 
Onions,  wild,  684 
Ononis  repens,  577 
Orange,  90,   133,  134 
Orchids,  631 
Origin    of    species    (Darwin) 

109 
Orobanche,  220 
Othonna  crassifolia,  443 
Otin,  618 
Oviedo,  89 


Paeonia    corallina    leiocarpa, 

126 
Paillat,  618 
Pangenes,   306 
Pangenesis,    306,   689 
Panicum,  105 
Pansies,   640 
Pansy,   118,    121 
Papaver  alpinum,  139 

bracteatum,  661 

bracteatum      monopetalum, 
661 


840 


Index 


commutatum,  357 

dubium  glabrum,  126 

hyhridum,  663 

somniferum   Danehrog,    163 

somniferum     monstruosum, 
371 

somniferum     polycephalum, 
371 
Parris,  754 
Paisley 

crisped,  158,  181 
Parsnip,   water,   457 
Pea-family,  344 
Peach,  138,  226,  240 
Peach-almond,  769 
Pears,   79,  90,   134,   147,   152, 

203,  283 
Pearson,  Karl,  716 
Peas,  sugar,   135,   158 
Pedicularis,  410 

palustris,  410 
Pedigree-culture,  109 

experimental,  547 
Pelargonium,  272,  355 
Peloria,  definition  of,   164 
Peloric  toad-flax 

first  record  of,   466 

origin  of,  459,  464,  473 

sterility  of,  467 
Pelorism 

Antirrhinum     majus      (see 
snapdragon). 

Digitalis  purpurea,   483 

Gloxinia,  484,  485 

labiates,  486 

Laburnum,    485 

Lamium,   486. 

Linaria,  see  Toad-flax 

Linaria    dalmatica,    482 

Linaria   vulgaris,  464 

orchids,    479,    486,    487 

Salvia,  486 
Scrophularia  nodosa,  486 

snapdragon,  481 

toad-flax,    459-487 

Tropaeolum  majus,  485 

Uropedium  Lindenii,  487 

wild  sage,  486 
Feltaria  alUacea,  663 


Pennywort,   marsh,   668 

Penzig,  638 

Periodicity,  law  of,  365,  368, 

721,  722 
Periods,  mutative,   706,   708 
Periwinkles,   322 
■Persicaria,    water,    433,    434, 

435,  643 
Petalomany,  330 
Petunia,  491,  626 
Phacelia,  420,  422,  820 
Phaseolus  lunatus,  592 

multiflorus,  202 

nanus,   202 
Phleum  alpinum,  696 
Phlox,  232 

drummondi,  161 
Phyllonoma  ruscifolia,   676 
Physiologic    units,    144,    153, 

249 
Picris  hieracioides,  411 
Pimpernel,    scarlet,    162 
Pinacothec,  Munich,  164 
Pine,  368,  804 
Pine-apples,  90,  134 
Pinks,    178 
Pinus  sylvestris,  368 
Pistillody     in     poppies,     369, 

370,  372 
Pitcher-plants,  671 
Plankton,   711 
Plantago,  53 

lanceolata,  520,  671,   684 
Plantain,  684 
Plater,  610 
Plum,  79,  134,  769 

beach,  58 

Japanese,   58 

purple-leaved,  619 
Plusia,  204 

Poa  alpina  vivipara,  684 
Podocarpus  koraiana,   169 
Polemonium    coeruleum,   282 

coeruleum  album,  200 

dissectum,   161,  202 
Poly  gala,  242 
Polygonum    amphibium,   433 

var.    natans    Moench,    433, 
434 


5 


^ 


Index 


841 


var,  terrestris  Moench,  433, 
434 

Convolvulus,   419,    424 

viviparum,  684 
Polymorphy,  188 
Pomegranate,  90 
Pond-lily,    yellow,    268 
Poplar,    fastigiate,    623,   624 

Italian,  623 
Populus  italica,  623 

nigra,  624 
Poppy,  146,  151,  152,  163,  165, 
241,  356,  640,  723 

"Danebrog,"    283,    291 

garden,   661 

"  Mephisto,"    283,    291 

opium,  89,  189,  195,  198, 
282,  291,  369,  371,  373, 
379,  383,  391,  405,  406, 
420,  452,  720,  789 

pistillody  in,  369 

pistilloid,  508 

polycephalous,  405 
Potatoes,  765,   810 
Potentilla  Tormentilla,  53 
Pre-Linnean  attitude,  2 
Primrose,  268,  372,  410 

evening    ( see   evening-prim- 
rose ) . 
Primula  acaulis,  52,  633 

elatior,  52,   633,  635 

grandiflora,  268 

imperialis,  697 

japonica,    410 

offioinalis,  52,  268,  633,  635 

variabilis,  268 

veris,  52,  633,  634 
Prodromus      (De      Candolle) 

370 
Progression,     430,    705,     774, 
775,   777,  779,  805 

in  evolution,  630 
Propagation 

asexual,  745,  751,  766,  767, 
770,  774,  777 

sexual,  745,  777 

vegetative    (see  asexual). 
Proskowetz,  Em.  von,  70 
Prototype 

definition  of,  170 


Prunus,  52 

cerasifera,  619 

Mahaleb,   617 

nana,  613 

maritima 

Padus,    617 

Pissardi,    619 

variation  in,  56 
Pyrethrum   roseum,  511 
Pyrola,    222,    661 

Q 

Quartile,  736,  737,  767 
Quercus  pedunculata  fastiga- 

ta,  596 

Quetelet's  law,  463,  716,  717, 

725,    730,    734,  738,    748, 

753,    759,    767,  775,    779, 

780,  806 


R 


Races,     inconstancy     of     im- 
proved, 770-797 
Raciborsky,   682 
Radishes,  325,  806 
Ragwort,   tansy,    157 
Raisins,    134 
Rameses,  697 
Ranunculus,  331 

acris,  331 

arvensis,  283 

arvensis  inermis,  125 

asiaticus,  241 

bulbosus,  357,  410,  740 
Ra-n-Woser,  King,   104 
Raphanus  Raphanistrum,  202, 
424,   520 

caudatus,  202 
Rasor,  John,  588,  589 
Raspberry,  268,  768 

"Phenomenal,"  268 

"  Primus,"  269 

Siberian,  269 
Ratzeburg,  467 
Raunkiaer 

on  variation  in  Taraxacum, 
60 
Recessive    character,    280 


842 


Index 


Regression,  95,  630,  705,  732, 

774,  775,  777,  779,  789 
Retrogression,  430 
Reversion,    155,    167,    170 

atavistic,    199 

bud,  167,  168,  183,  284 

definition  of,   166 

seed,  175 

significance  of,  215 
Reversionists,   156 
Rhingia,    173 
Rhododendron,    804 
Rhododendron       ferrugineum, 
267 

hirsutum,  267 

intermedium,  267 

ponticum,  661 
Rihes,  170,  226,  625 

aureum,  270 

sanguineum,    166,  270 

scarlet,  166 

Vva-crispa,    140 
Rice,  crown,  133 
Ricinus,   139 

Rimpau,    69,    70,    94,   98,   99, 
207,    792,    803,   810,   811, 
812,  813 
Risler,  99,  207,  803 
Rivett,  98,  99 
Riviere,   134 

Robinia     Pseud-Acacia,     133, 
343,  664 

Pseud-Acacia      monophylla, 
196 
Robinson,  B.  L.,  590 
Rose,  126,   127,  152,  178,  233 
Rose,   corn,   282 

moss,  627 
Rose,  610,  611 
Rosen,   38,  47 
Rothamstead,  102 
Rubia  tinctorum,  410 
Rubus  flexuosus,  663 

fruticosus,  268 

idaeus,  268 

odoratus,  663 
Rudberg,    466 
Rumex  scutatus,  139 
Ru^cuSy  676 


Rye,  105,  410,  453,  810,  813, 
821,  822 


S 


Sagina  apetala,  52 

patula,  52 
Sagittaria  japonica,  671 
Salix  alba,  267 
Ehrhartiana,  267 
pentandra,  267 
Salpiglossis  sinuata,  622 
Salter,    Bell,    269 
Salvia,  242 

pelorism    of,    486 
sylvestris,  161 
Sambucus      niger      laciniata, 
616 
racemosa   laciniata,   616 
Saponaria  calabrica,  612 

officinalis,  409,  663 
Sarracenia,  672 
Saxifraga  crassifolia,   366 

umbrosa,  684 
Saxifrage,  366 
Scabiosa,  514 
Schimper,   663,  738 
Schimper   (Braun  and),  494 
Schindler,   70 
Schlanstedt,  822 
Schubeler,  805 
Scirpus  lacustris,  684 
Scrophularia  nodosa,  pelorism 

of,  486 
Sea-burdock,    139 
Secale  Cereale,  410 
Seden,  273 
Sedum,    165 
Seed-variation,  750 
Sekera,  578 

Selection,  108,  111,  114,  390, 
399,  743,  751,  789,  790, 
792,  793,  794,  797,  799, 
800,  801,  804,  806,  807, 
808,  813,  825 
artificial  (see  Artificial  se- 
lection) . 
between    species,    744,    800, 

801 
continuous,    778,    784,   786, 


I 


Index 


843 


787,   788,   795,   797,   805, 
806,  825 
double  meaning  of,  109,  110 

individual,   801 
intra-specific,  741,  744,  749, 
751,    800,    801,    802,   805, 
825 
natural   (see  Natural  selec- 
tion ) . 
repeated    ( see  continuous ) . 
species,  743,  744 
within  the  species,  744,  800 
Self-heal,  268 

white,  201 
Sempervivum   tectorum^   370 
Senecio  jacdbaea,  157 

vulgaris,  132 
"Sereh,"  756 
Series,    The,    of    Braun    and 

Schimper,  494 
Seringe,  523 
Setaria,  105 

Shepherd's    purse,    582,    638, 
639 
Heeger's.  638,  684 
Shirreff,     Patrick,     107,     108, 
109,    110,    111,    113,    114, 
115,  116,  743 
Silene  annulata,  663 
Armeria,  161,  232,  282 
rosea,  163 
conioa,   419 
connoidea,  419 
Silverchain,  133 
Sinning,  668 
Sisymhrium,  637 
hirsutum,  637 
officinalis,  637 
supinum,  637 
Sium  latifolium,  457 
Smith,  667 
Snakeroot,   674 
Snapdragon,     150,     152,    281, 
315,    316,    321,    324,    326, 
420,  452 
"  Black     prince "     variety, 

782 
"Brilliant,"   151 
"Delila,"   151,   195,  782 


"Firefly,"  195 
"Fleshy,"   151 
peloric,  race  of,  781 
self-fertility  of,  781 
striped,    740 
yellow,  194 

Soapwort,  409 

Solanuni,  655,  685 
Dulcamara  tomentosum ,  125 
nigrum  chlorocarpum ,  298 

Solms-Laubach,  104,  107,  582, 
583,  584 

Soltwedel,  755 

Sophora     japonica     pendula, 
617 
japonica,  136 

Sorbus   Aucuparia,   342 

Species 

artificial  character  of,  36 
constancy  of,  693,  697 
crosses    of    with    varieties, 

247,  277,  278,  281 
dimorphous,  447 
elementary      (see     Elemen- 
tary species), 
experimental    study    of,    37 
meaning  of  term,   10,   122 
origin  of,  307,  461,  550,  560, 

825 
origin    of,    easily    observed, 

26 

polymorphous,  700 
selection  between,  744 
selection  within,  744 
smaller      (see     Elementary 

species), 
spontaneous  cross,  209 
survival  of,  799 
systematic,    see    Systematic 

species 
two  sorts,  12 

Variety   vs.,    122,    154,   220 
hybrid    (see  Hybrids). 

Specific  marks,  origin  of,  275 

Spath,   619 

Spergula  media,  53 
salina,  53 

Spinage,   139,   158,  419 

New   Zealand,    162 

Sport,  111,  310,  311,  316 


844 


Index 


Sports,  191,  715,  689 

bud,  427 
Sprenger,  610^  611 
Stability,  155 
Stahl,  611 
Stellaria     Holostea     apetala, 

585 
Stocks,  146,  322,  328,  329,  332, 

334,  336,  338,  432 
Stock 

"  Brompton,"   329 

chamois-colored,  198 

"Queen,"  324 

white,   160 
Stork's-bill,     white     hemlock, 

161 
Strasburger,    196,   448 
Strawberry,   158,   266,  343 

"  Gaillon,"  135 

"Giant   of    Zuidwijk,"    614 

one-leaved,   164,  596,  666 

white,  158,  165 
Striped  flowers,  309,  374,  431, 
606,  607 

races,  types  of,  328 
Struggle    for    life,    674,    571, 
682,    702,    799,   803,    824, 
825 
St.  Johnswort,  725 
St.  Sebastian,  164 
Sub-species      (see     also     Ele- 
mentary    species),     224, 
225 
Sugar-beets     (see    Beets,    su- 
gar). 
Sugar-cane,  731,  752 

"Black    Manilla,"   753 

"Cheribon,"    753,    755,    756 

"Chunnic,"   753 

"Hawaii,"  755,  756 

seeds  of,  754 

"  White  Manilla,"  753 
Sundew,  268 
Sunflower,  410,  425,  820 
Sweet-flag,  222 
SAveet-pea,    160,    776 
Sweet  William,  163,  282,  322, 
648 

twisted  variety 
Syncotyls,  417,  424 


Syringa  vulgaris  azurea  pie- 

na,  763 
Systematic    species,     12,     64, 
101,   128 
nature  of,  54,  63 
Systematic  units,  61,  91 


Tagetes  africana,  510 

signata,  612 
"Talavera   de  Bellevue,"   97 
Tanacetum  vulgare,  131,  132, 

236 
Tansy,   131,  132,  236 
Taraxacum,  125,  126 

officinale,   59,   411 
Tares,   105 
Taj)us,  136 

haccata,  169 

haccata  fastigiata,  170,  618 

minor,   169 
Teasels,    402,    642,    645,    674, 
675 

twisted,  405,  412,  446,  447, 
643,  646,  647,  648,  819 
Tetragonia    expansa,    162 
Theatre    d'Agriculture,    72 
Thibault,   618 
Thomson,    Sir    William     (see 

Kelvin,  Lord). 
Thorn-apples,    139,    142,    143, 
145,  238,  283,  300,  453 

thornless,  234 
Thorn-broom,  457 
Thrincia  hirta,  411 
Thuret,  38,  47,  49 
Thyme,  white  creeping,  201 
Thymus    Serphyllum    album, 
201 

vulgaris,  577 
Tili<i  parvifolia,  355,  669 
Toad-flax,  267,  282,  707 

cross   pollination  of,   471 

experiment  with,  described, 

468 
invisible    dimorphous    state 

of,  470,  471,  478 
latent  tendency  to  mutation 

in,  479 


Index 


845 


peloric,    see    Peloric    toad- 
flax, 

sterility  of  mutants,  477 

unusual  pelorism,  486 
Tomato,  653 

«  Acme,"  656,  657 

"  Mikado,"  654 

mutation  of,  655 

upright,  654 

"Washington,"  657 
Tournefort 

author  of  genera,  33 
Tracy,  W.  W.  592 
Trees,   genealogic,   707,   708 
Trieotyls,   416,   418,   419,   420 
Trifolium  incarnatum,  353 
Triticum   dicoccum,   105 
Tropaeolum,  193,  668 

majus,  pelorism  of,  485 
"True  Exercises  with  Plants" 

(Hunting),   490 
Tulips,  149,  178,  274,  323 

black,  620 
Turnip,  244,  621 
Twisted  stems,  402,  403,  405, 

413 
Twisted  varieties 

atavists  of,  406 


U 


Ulex  europaeus,  140,  217 
Ulmus  pedunculata,  615 
pedunculata       urticaefoUa, 

615 
Umbellifers,  457 
Umhilicus,  669 
Unger,  105 
Unit-characters,  249,  261,  306, 

307,    313,    658,    689,    715, 

716 
Urban,   265 

Uropedium  lindenii,  487 
Utility,  685,  724 
Utricularia,  672 


Vaccinium  Myrtillus,  577 
Valerian,  402,  409    648 


twisted,  403 
Valeriana  officinalis,  402 
Vallisneria,  684 
Van  den  Berg,   625 
Van  de  Water,  614 
Van  Mons,  76,  77,  78,  806 
Variability     (see    also     Fluc- 
tuation), 188,  190,  191 

analogous,  244 

apple,  75 

asexual,  320 

correlative,  142,  143,  148, 
167 

cultivated  plants,  66 

embryonic,  770,  771,  814 

ever-recurring,    190 

fluctuating  (see  also  indi- 
vidual), 62,  142,  190, 
233,  375,  416,  454,  698, 
759,  762,  765,  766,  767, 
770,  771,  789,  805,  814 

fluctuating  vs.  mutability 
568 

homologous,    244 

individual  (see  also  fluc- 
tuating), 190,  716,  718, 
746,  749,  770,  814 

influence  of  mutation  on, 
335 

kinds  of,  715 

nutrition  and,  390,  391, 
719,  771 

parallel,  243 

partial,  440,  444,  718,  746, 
748,  753,   814,  816 

repeated,  242 

restricted,  598 

sectional,   317 

sexual,   320 

sovirces  of,  758 
Variation 

bud,  176,  178,  180,  284, 
317,  318,  321,  338,  427, 
750 

definition  of,   188 

partial,  788,  789 

seed,  750 

spontaneous,  191 

use  of  term,  189 
Variegation,  426,  427 


846 


Index 


Varietal     marks,     origin     of, 

275 
Varieties,    84,    95,    126,    127, 
128,   129,  132,   142 

broom-like,    618,    624 

constancy  of,  532 

constant,   135 

crosses  of  species  with,  247, 
277,  278,  281  ^ 

elementary   species  vs.   459 

ever-sporting,  178,  309, 
310,  311,  312,  313,  321, 
324,  328,  329,  332,  333, 
334,  350,  358,  365,  368, 
372,  399,  413,  420,  430, 
431,  432,  434,  445,  606, 
607,  628,  740,  789,  790, 
795 

fasciated  (see  Fasciated 
stems) . 

groups  of,   606 

horticultural,   607,   609 

hybrid,   122,   190,  608 

hybrids  of,  210,  254,  255 

inconstant,  135,  154,  155, 
161 

mutation   of,   141 

negative  ( retrogressive ) , 
131,  132,  134,  224,  226, 
238,  245,  277 

positive,  131,  132,  134,  224, 
238,  245 

pure,  122,  190 

retrograde,  14,  15,  16,  95, 
121,  208,  430,  435,  606, 
607 

retrogressive  ( see  nega- 
tive ) . 

seed,  123 

single,  191 

spontaneous  crosses,  209 

sporting    (see    inconstant). 

stability  of,  207 

sterile,  622 

types  of,   142 

variable,  606 

vegetative,  123 

weeping,  617 
Variety,  130 

definition  of,  11,  12 


elementary  species  vs.   141, 
152,    154,   224,   243,   247, 
251 
origin  of,  141,  152,  224 
use  of  term,   189,  435 
Variety-testing,    95,    97,    116, 

119,  743,  799,  825 
Varro,   106 
Veitch  &  Sons,  273 
Venus'   looking-glass,   367 
Verlot,  186,  612 
Vernon,   133 
Vernonia  cinerea,  450 
Veronica   longifolia,   282,  284 
scutellata,  139 
spicata  nitens,  126 
Viburnum  Opulus,  134,  239 
Vicinism,   185,   188,  203,  205, 
206,  213,  214,  776 
definition  of,   188,   192,  606 
Vicinist,  199,  201 
Vicoa  auriculata,  450 
Victoria  regia,  668 
Villars 

on  Draha  verna,  49 
Vilmorin,  570,  607,  612,  622, 
661,   662,   773,    775,   776, 
792,   795,    796,    797,   806, 
807,  810,  813,  818,  820 
Vilmorin,    Louis    de,    72,    92, 
93,  97,  108,  109,  110,  114, 
185,  818 
Vilmorin,  Messrs.,  322 
Vinca,  242,  490 

minor,  322 
Vine,  parsley-leaved,   179 
Viola,  126,  546,  547,  693 
agrestis,  45 
alpestris,  40 
altaioa,  39 
anopetala,  44 
arvensis,  39,  40,  41,  44 
curtisepala,  45 
striolata,  45 
aurohadia,  44 
calcarata,  39 
cornuta,  39,  281 
lutea,   38 
lutescens,  44 
nemausensis,  45 


: 


Index 


847 


ornatissima,  4l4: 

palescens,  45 

patens,  45 

roseola,  44 

segetatis,   45 

stenochila,  41 

tricolor,  38,  40,  41,  44,  46 
ammotropha,  41 
coniophila,  41 
genuina,   42 
versicolor,  42 
Violets,  63,  232,  233,  490 
Violet,  dame's,  322,  323,  411 

long-spurred,   281 
Virgil,   105,  106,   108 
Viscaria   oculata,   4,   648,  821 

twisted  variety,  408 
Vitis,  52 
Volckamer,  228 
Von  Loehow,  821,  822,  823 
Von  Rliraker,  94 
Von  Wettstein,  448,   805 
Vrolik,  164,  483 

W 

"Waare  Oeffeninge  der  Plan- 
ten''    (Munting),   490 
Wallace,  5,  7,  8,  30,  205 
Wall-flower,    370,    371 
Walnut,  243,  766 

cut-leaved,    616 

one-bladed,  666 
Water-lilies,  668 
Weber,   228 
Weeping-willow,   180 

crisped,   181 
Weigelias,  740 
Wellingtonia,  618 
Wheat,  96,  98,  105,  113,  119, 
283,  810,  823 

bearded,  98 

"Blue-stem,"  117 

"  Galland,"  100,  207 

"Hopetown,"  112,  113 

"Hunter's,"  HI,  113 
"Minnesota   No.    169,"    117 
"  Mungoswell's,"  110,  111 


"Pedigree,"   109 

"  Pringle's,"  114 

"  Rivett's    bearded,"    207 

"  Sheriff's      bearded      red," 
114 

"  Sheriff's    bearded    white," 
114 

"White    Hunter's,"    113 
Wheat-ear  carnation,  227 
White,  C.  A.,  656,  657 
White  varieties,  577 
Whitlow-grasses,  63,  118,  119 
Whorls,  ternate,  684 
Wild   sage    (see   Salvia). 
Willdenow,  468,  666,  667 
Williamson,  491 
Willows,  135,  267 
Willow 

weeping    (see   Weeping-wil- 
low ) . 
Willow-herb,  268,  269,  683 
Wintercress,  427 
Wintergreen,  661 
Wittmack,  682 
Wittrock,  38,  40,  41,  42,  43, 

44,  45,  46 
Wooton,  E.  0.,  140 
Wormseed,  638 


Xanthium   canadense,    140 
commune,  140,  152,  591 
commune    Wootoni,   22 
Wootoni,  140,  152,  591 


Yarrow,  131,  132 
Yew,  136,  169 
pyramidal,  618 


Zea  Mays  cryptosperma,  641 

tunicata,   641 
Zinnia,  490 
Zioberg,  466 
Zocher  &  Co.,  230 


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